Nuclear Structure 2026

Jul 26, 2026, 8:00 a.m. → Jul 31, 2026, 6:30 p.m. US/Pacific

Fletcher Challenge Canada (Simon Fraser University Harbour Centre)

Corina Andreoiu (Simon Fraser University), Krzysztof Starosta (Krzysztof Starosta)

Please beware of phishing attempts - all communication for NS2026 will come from SFU! We will also NOT ask you to sign any forms online or provide any information!

We are looking forward to seeing you at the Nuclear Structure 2026!

Where Cutting-Edge Nuclear Physics Meets Stunning Vancouver!

Registration desk will be open on Sunday from 16:00 -18:00 pm at 

SFU Harbour Centre, 515 West Hastings St., Vancouver

_{We respectfully acknowledge the unceded traditional territories including, the Sḵwx̱wú7mesh Úxwumixw (Squamish), səlilwətaɬ (Tsleil-Waututh) and xʷməθkʷəy̓əm (Musqueam) Nations, on which SFU Vancouver is located.}

Get ready for an unforgettable experience at the 20^th biennial Nuclear Structure Conference, proudly hosted by Simon Fraser University and TRIUMF from July 27 to July 31, 2026. Set against the breathtaking backdrop of Vancouver, this prestigious event will gather the brightest minds in nuclear structure physics from around the world.

The conference will spotlight groundbreaking research and development in both experimental and theoretical nuclear structure physics, diving deep into the fascinating properties of nuclei at the far reaches of isospin, excitation energy, mass, and angular momentum.

We are curating an action-packed, inspiring program that includes:

• A warm welcoming reception
• A fun conference dinner
• An interactive poster session
• A fascinating tour of TRIUMF, Canada’s national particle accelerator centre
  • Or, a free afternoon to explore the wonders of Vancouver and its spectacular surroundings!

Join us for an extraordinary week of discovery, networking, and inspiration. 

Nuclear science and the vibrant charm of Vancouver await you—don’t miss out!

Local Organizing Committee:

Corina Andreoiu (SFU), co-chair

Gordon Ball (TRIUMF)

Barry Davids (TRIUMF)

Iris Dillmann (TRIUMF)

Stephan Malbrunot-Ettenauer (TRIUMF)

Paul Garrett (Guelph)

Adam Garnsworthy (TRIUMF)

Gwen Grinyer (Regina)

Greg Hackman (TRIUMF)

Kris Starosta (SFU), co-chair

Carl Svensson (Guelph)

 

NS2026 Poster May 27.jpg

Second Circular Nuclear Structure 2026.pdf

Sun, July 26

4:00 p.m. → 6:00 p.m. Registration

Mon, July 27

9:00 a.m. → 10:30 a.m. Monday Morning Early Session: (Chair: Ritu Kanungo)

9:00 a.m. Welcome

9:10 a.m. EDI in Physics Collaborations

Equity, Diversity, and Inclusion have become increasingly important topics discussed in society. Physics collaborations are unique organizations that can play an important role in advancing these ideas. Host laboratories can also play a role with the policies they have for collaborations building and operating experiments on their sites. In this talk, I will discuss the current situation in terms of equity, diversity, and inclusion in nuclear and astroparticle physics, highlighting progress and challenges. I will present some of the work that has been done in physics collaborations and laboratories to advance these ideals.

Speaker: Dr Erica Caden (SNOLAB)

9:40 a.m. Nuclear Shell Model on Current and Future Quantum Computers

Quantum computers hold the promise of being a transfomrational in application to many spheres of human endeavour. In particular, the simulation of many-body quantum systems, such as nuclei, is naturally amenable to quantum computation. This is due, in part, to the exponential scaling of Hilbert space size as the number of quantum bits (qubits) grows linearly. This mirrors the exponential growth of Hilbert space size as the number of particles or orbitals in a nuclear problem grows linearly.

Real quantum computers now exist. They have some drawbacks, including short coherence times limiting their ability to deliver the hoped-for breakthroughs, yet first results show promise and algorithmic developments are underway to prepare for future "fault-tolerant" quantum computers which are on the road map of the quantum hardware companies.

In this contribution we present our current results for nuclear shell model developments in simulation 1, along with calculations on real quantum hardware 2 - with nuclei up to ²¹⁰Pb calculated on 29 qubits on the IBM_pittsburgh machine. We then go on to show preparatory work for future hardware, in which we use tensor network methods to produce states with >50% overlap with exact solutions on 76-qubit systems, equivalent to a shell model calculation with matrix dimension ~10¹¹ in ¹⁴³Ce. We use tensor network to quantum circuit compilation techniques to prepare algorithms ready to go on near-future fault-tolerant machines 3.

Work in collaboration with B. Bhoy, C. Sarma, and J. Gibbs at the University of Surrey

1 B. Bhoy and P. D. Stevenson, New. J. Phys. 26, 075001 (2024)
2 C. Sarma and P. D. Stevenson, Discov. Quantum. Sci. 2, 6 (2026)
3 J. Gibbs, L. Cinzio, C. Sarma, Z. Holmes, and P. Stevenson, arXiv:2603.11156 (2026)

Speaker: Prof. Paul Stevenson (University of Surrey)

10:05 a.m. Halo Nuclei from Ab Initio Nuclear Theory

A realistic description of halo nuclei, characterized by low-lying breakup thresholds, requires a proper treatment of continuum effects. We have developed an ab initio approach, the no-core shell model with continuum (NCSMC), capable of describing both bound and unbound states in light nuclei in a unified way. With chiral two- and three-nucleon interactions as the only input, we can predict structure and dynamics of halo and other light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces. We review NCSMC calculations of weakly bound states and resonances of exotic halo nuclei 6He, 8B, 11Be, and 15C. For the latter, we discuss its production in the capture reaction 14C(n,γ)15C. We highlight challenges of a description of 6He as a Borromean n-n-4He system. Finally, we present calculations of excited states in 10Be exhibiting a one-neutron halo structure and a large scale no-core shell model investigation of 11Li as a precursor of a full n-n-9Li NCSMC study.

Speaker: Petr Navratil (TRIUMF)

10:30 a.m. → 11:00 a.m. Coffee break

11:00 a.m. → 12:30 p.m. Monday Morning Late Session: (Chair Ben Kay)

11:00 a.m. The Standard Model and Beyond from a Nuclear Structure Perspective

At the heart of particle physics lies the the Standard Model, one of the most (if not the most) successful theories of all of science, which describes the fundamental building blocks of the Universe and how they interact with each other. However, even with all the successes of this theory, mounting evidence tells us that it is at best incomplete. Nonetheless, after years of searches at particle accelerators, direct observation of any process Beyond the Standard Model still eludes us. In this talk, I will present how developments in nuclear theory can allow another, less expensive, avenue to become competitive in those searches: the high-precision measurement of low-energy processes inside the atomic nucleus. I will focus of recent developments that have allowed the rigorous quantification of uncertainty of nuclear structure properties required to interpret these searches.

Speaker: Antoine Belley (Massachusetts Institute of Technology)

11:30 a.m. Measuring Electroweak Nuclear Properties with Single Molecular Ions in a Penning Trap

The NEPTUNE collaboration is developing a new Penning ion trap aimed at precision spectroscopy of symmetry-violating electroweak effects using single trapped molecular ions [1]. The inherent strong magnetic field for ion confinement can be used to Zeeman-shift two opposite-parity molecular states into near degeneracy, increasing sensitivity to parity-violating nuclear properties by more than 11 orders of magnitude [2]. This approach is therefore expected to enable extremely sensitive measurements of symmetry-violating nuclear properties, such as anapole moments, across a wide range of nuclei. This contribution will summarize the current status of the cryogenic Penning trap for measurements in SiO⁺ and outline future prospects for the technique.
[1] J. Karthein, S. Udrescu, S. Moroch et al. Phys. Rev. Lett. 133, 033003 (2024)
[2] Altuntas, E. et al. Phys. Rev. Lett. 120, 142501 (2018)

Speaker: Charlotte Konig (Texas A&M University)

11:50 a.m. Exploring the origin of the reactor antineutrino anomaly: high-resolution β-decay study of 92-Rb

The $\beta$ decay of neutron-rich nuclei produced via fission processes from nuclear reactors have played a crucial role in developing our understanding of neutrinos within the standard model of particle physics. Reactor antineutrino experiments are unique in providing intense fluxes of with pure electron flavour ($\bar{\nu_e}$) within an MeV-scale energy range which are exploited to perform three-neutrino-flavour oscillation experiments [1] and the search for a fourth-flavour sterile neutrino leading to new physics beyond the standard model. The Reactor Antineutrino Anomaly (RAA) refers to an ~6% deficit in antineutrino measured detection rates [2] and an excess of antineutrinos at 5-7 MeV known as the ‘shoulder’ when compared to state-of-the-art Huber-Muller model predictions [3,4]. This anomaly has prompted a flurry of activity from both theory and experiment over the past 15 years to resolve this disagreement and significant progress has been achieved. These antineutrinos are produced via the $\beta$ decay of fission fragments and therefore, the origin of the RAA lies in the details of the $\beta$-decay processes. Despite their importance, much of the existing $\beta$-decay data is unsatisfactory, and improvements are essential to the future of reactor antineutrino experiments.
The $\beta$ decay of $^{92}$Rb is one of the main contributors to the reactor high-energy antineutrino spectrum and consequently an important contributor to the RAA. Recent studies of this decay using Total Absorption Spectroscopy (TAS) [5,6] reveal significant discrepancies with significant additional feeding to high-lying levels when compared with previous work utilising High-Resolution Spectroscopy (HRS) performed in the 1970s. This discrepancy can be attributed to the Pandemonium effect leading to incorrect $\beta$ feeding measurements in the HRS data which in turn lead to incorrect predictions of the antineutrino flux produced. While the TAS method is excellent at obtaining reliable $\beta$ feeding measurements, it is a limited probe of nuclear structure and exploiting both methods is essential to obtain a comprehensive understanding of this decay.
We have thus revisited the $\beta$ decay of $^{92}$Rb ($J^{\pi}=0^-, Q_{\beta}=8.1$ MeV) with the GRIFFIN spectrometer at TRIUMF that consists of up to 16 Compton-supressed HPGe clover detectors. Due to the high intensity of radioactive beam of $^{92}$Rb and the high efficiency of GRIFFIN for detecting $\gamma$ rays, we have obtained an unparalleled picture of $^{92}$Sr with over 180 levels populated and over 850 -ray transitions placed within the level scheme up to and beyond the neutron separation energy of $^{92}$Sr. The $\beta$ feeding of $^{92}$Sr measured in this work compare very well with the most recent TAS study demonstrating a significant suppression of this Pandemonium effect.
This work reveals the $\beta$ decay of $^{92}$Rb populated numerous high-lying levels in $^{92}$Sr. These levels are situated in the energy region of the Pygmy Dipole Resonance (PDR) that manifests as an enhancement of electric dipole strength at the low-energy tail of the Giant Dipole Resonance (GDR) near the neutron separation energy of $^{92}$Sr. The PDR is interpreted as an out-of-phase oscillation between the neutron skin and an isospin saturation core; however, this remains a matter of debate. The new information of nuclear levels in $^{92}$Sr from our study demonstrate the possibility in exploiting $\beta$ decay to investigate the PDR in nuclei and provide a complementary approach to existing techniques.

[1] T. Araki et al. (KamLAND Collaboration), Phys. Rev. Lett. 94, 081801 (2005)
[2] F. P. An et al. (Daya Bay Collaboration), Phys. Rev. Lett. 116, 061801 (2016)
[3] P. Huber, Phys. Rev. C 84, 024617 (2011)
[4] T. A. Mueller et al. Phys. Rev. C 83, 054615 (2011)
[5] B. C. Rasco et al. Phys. Rev. Lett. 117, 092501 (2016)

Speaker: Pietro Spagnoletti (University of Liverpool)

12:10 p.m. Nuclear structure from higher-order multipole moments

Electromagnetic transition rates and multipole moments are crucial observables for understanding and interpreting nuclear structure. While $E2$ transitions tend to be dominant among the low-excitation states of broad ranges of nuclei, particularly as collectivity emerges, and the magnetic moment is sensitive to the structure of an individual state, giving a measure of how the nucleus is carrying its angular momentum, higher-order moments are also important despite data being relatively rare. One example is the unique $E6$ transition in $^{53}$Fe [1] where it was found that the effective charges appropriate for higher-multipolarity $E4$ and $E6$ transitions differ from those applicable to $E2$. It can be said that the higher-multipolarity electric (magnetic) transitions help reveal the physics hidden in the effective charges ($g$ factors).

The data on magnetic octupole moments, which are fairly rare, have been compiled recently by Bofos and Mertzimekis [2]. It will be shown that the $M3$ magnetic octupole moment, in most of the cases that have been measured, can be estimated with considerable accuracy from the measured magnetic dipole ($M1$) moment. The level of agreement is a surprise, given that the core-polarization mechanism associated with the effective $g$ factors in the $M1$ operator is not expected to be applicable for the $M3$ operator.

Implications and possible explanations, along with some strategies for further investigation, will be discussed. For example, high-precision laser spectroscopy could add to the $M3$ moment data base [3,4] and it can be anticipated that a renaissance in muonic-atom x-ray spectroscopy [5] will yield new data on higher-order nuclear moments.

References
[1] T. Palazzo et al., Phys. Rev. Lett. 130 (2023) 12203.
[2] S. Bofos, T.J. Mertzimekis, Atomic Data and Nucl. Data Tables 159 (2024) 101672.
[3] V. Gerginov, A. Derevianko and C.E. Tanner, Phys. Rev. Lett. 91 (2003) 072501.
[4] R.P. de Groote et al., Phys. Lett. B 827 (2022) 136930.
[5] R.J. Powers et al., Phys. Rev. Lett. 34 (1975) 492.

Speaker: Gregory Lane (The Australian National University)

12:30 p.m. → 2:00 p.m. Lunch Break

2:00 p.m. → 3:30 p.m. Monday Afternoon Early Session: (Chair Francesco Recchia)

2:00 p.m. Recent Results with the FDSi at FRIB and the new GROVER Detector

A brief overview of recent results from the FRIB Decay Station initiator (FDSi) will be presented. An emphasis will be placed on new gamma-decaying isomers. These isomers provide highly constrained structure possibilities for each region and important landmarks for future exotic beam studies. Finally, a brief overview of the new DEGA-FDS prototype, GROVER, will be presented. The new detector houses four p-type point-contact HPGe crystals in a single cryostat, combining design elements from both LEGEND and GRETA.

*This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.

Speaker: James Allmond (ORNL)

2:30 p.m. Two Neutrons, Three Discoveries: Using Two-Neutron Energy Correlations to Probe Nuclear Structure from 134In Decay

Exotic, neutron-rich nuclei are a testing ground for the evolution of nuclear structure away from stability [1]. As radioactive beam facilities extend isotope production toward the neutron dripline [2-3], it is paramount that experimental efforts follow into this less-explored region of the nuclear chart to fully exploit its discovery potential. In these nuclei, beta-delayed single- and multi-neutron emission often dominates decay paths toward stability [1]. Neutron spectroscopy combined with gamma-ray measurements is necessary to uncover the full picture. Nuclei such as those southeast of 132Sn in the chart of nuclides are less affected by the typical experimental challenges of neutron detection; studying the decays of near-doubly magic nuclei simplifies the analysis, as they populate nuclei with low nuclear level densities and strong single-particle character. In this regard, I will present results from the beta-delayed neutron spectroscopy of 134In performed at the ISOLDE Decay Station at CERN [4], using the Neutron dEtector with multi-neutron (Xn) Tracking (NEXT) array [5-6]. For the first time, energy correlations in two-neutron emission were exploited as a probe for nuclear structure. In the two-neutron emission channel from 134Sn, the population of the long-sought i13/2 neutron single-particle state was observed as an intermediate step, thereby pinning down the energy of the final elementary excitation in 133Sn between the N = 82 and 126 shell closures [7-10]. Furthermore, we find a significant discrepancy between the experimental neutron-branching ratios to this state and the predictions of the Hauser-Feshbach statistical model for spherical neutron emitters [11-12]. This result indicates that the Bohr assumption of the immediate formation of a compound nucleus following beta decay is not valid in this case and should be revisited, with important implications for future experimental studies.

References:
[1] M. R. Mumpower et al.; Progress in Particle and Nuclear Physics, 86 86-126 (2016)
[2] R. Catherall, W. Andreazza, M. Breitenfeldt, A. Dorsival et al.; J. Phys. G 44, 094002 (2017)
[3] V. Fedosseev, K. Chrysalidis, T. Day Goodacre, B. Marsh et al.; J. Phys. G 44, 084006 (2017)
[4] P. Dyszel, R. Grzywacz, Z. Y. Xu et al.; Phys. Rev. Lett. 135, 152501 (2025)
[5] J. Heideman et al.; Nuc. Instrum. Methods Phys. Res. A 946, 162528 (2019)
[6] S. Neupane et al.; Nuc. Instrum. Methods Phys. Res. A 1020, 165881 (2021)
[7] P. Hoff, P. Baumann, A. Huck; Hyperfine Interactions 129, 141 (2000)
[8] A. Korgul et al.; EPJ A 7, 167 (2000)
[9] K. Jones et al.; Nature 465, 454 (2010)
[10] J. Allmond et al.; Phys. Rev. Lett. 112, 172701 (2014)
[11] W. Hauser and H. Feshbach; Phys. Rev. 87, 366 (1952)
[12] C. Pruitt, J. E. Escher, R. Rahman; Phys. Rev. C 107, 014602 (2023)

Speaker: Peter Dyszel (University of Tennessee, Knoxville)

2:50 p.m. Erosion of the N=40 Subshell Closure: New Insights from 68Fe

Although the shell model is fundamental to our understanding of nuclear structure, the breakdown of traditional magic numbers far from stability provides insight into the nature of the underlying nuclear interactions and acts as a tool to test existing models. Islands of inversion (IoI) in the nuclear landscape are characterized by the presence of deformed multi-particle multi-hole (npnh) ground states instead of the (0p0h) configurations predicted by spherical mean-field calculations. This is typically driven by the strong nuclear quadrupole-quadrupole interaction that induces shape transitions, wherein these highly correlated “intruder” states become more bound than spherical ones.

In the N=40 region, the relatively large energy gap separating the pf shell from the $\nu g_{9/2}$ orbital points towards a strong sub shell closure at N=40 which has been supported by the observation of a high-lying 2$^{+}$ state and low B(E2) value in $^{68}$Ni (Z=28) [1]. However, systematics of E(2+) and B(E2) values have indicated a sudden increase in collectivity below Z=28 when approaching N=40, seen especially in the rapid drop of E(2+) in Fe (Z=26) and Cr (Z=24) isotopes [2,3]. This is attributed to the neutron occupation of intruder states from a higher shell, similar to the IoI around N=20 [4, 5]. Shape coexistence also manifests in nuclei at the boundaries of IoIs [6]. In the N=40 region, low-lying 0$^{+}$ excited states, which are traditional indicators of shape coexistence have been identified up to A=66 [7, 8]. In $^{68}$Fe, a state at 2035 keV is tentatively assigned as 0$^{+}$ or 2$^{+}$ and the confirmation of this spin would indicate whether this trend extends past N=40.

To explore these phenomena, an experiment was performed at TRIUMF-ISAC using the GRIFFIN spectrometer that utilized the $\beta$- and $\beta$n decay of $^{68}$Mn to populate excited states in $^{67,68}$Fe, $^{67,68}$Co and $^{67,68}$Ni. This experiment produced the highest-statistics data set to date for these isotopes. Consequently, we have greatly expanded the level scheme of $^{68}$Fe and measured key spectroscopic quantities. Angular correlation analysis performed using the 64 HPGe crystals of GRIFFIN has provided new information on the spin assignment of the proposed 0$_{2}^{+}$ state, resulting in a reinterpretation of shape coexistence in this nucleus. Furthermore, the first direct measurement of the lifetime of the 2$_{1}^{+}$ level in $^{68}$Fe was performed using $\beta\gamma\gamma$ fast-timing analysis, and B(E2; 2$_{1}^{+}$ $\rightarrow$ 0$_{1}^{+}$) was subsequently calculated. The associated nuclear structure implications and other results from the analysis will be presented and discussed.

[1] O. Sorlin et al. In: Phys. Rev. Lett. 88 (9 Feb. 2002), p. 092501.
[2] S. Naimi et al. In: Phys. Rev. C 86 (1 July 2012), p. 014325.
[3] M. Hannawald et al. In: Phys. Rev. Lett. 82 (7 Feb. 1999), pp. 1391 1394.
[4] S. M. Lenzi et al. In: Phys. Rev. C 82 (5 Nov. 2010), p. 054301.
[5] Y. Tsunoda et al. In: Phys. Rev. C 89 (3 Mar. 2014), p. 031301.
[6] M. Rocchini et al. In: Phys. Rev. Lett. 130 (12 Mar. 2023), p. 122502.
[7] Balraj Singh. In: Nuclear Data Sheets 108.2 (2007), pp. 197–364.
[8] S. N. Liddick et al. In: Phys. Rev. C 87 (1 Jan. 2013), p. 014325

Speaker: Rashmi Umashankar (TRIUMF)

3:10 p.m. First β-Decay Spectroscopy Measurements of ³¹F and ³⁷Na Using FDSi

The study of nuclear structure in regions of extreme neutron excess provides stringent tests of shell-model predictions. Experiments at the Facility for Rare Isotope Beams (FRIB) continue to explore nuclei at the limits of stability. On the neutron-rich side, crossing from $N = 20$ toward the $N = 28$ island of inversion, the isotopes $^{31}\mathrm{F}$ and $^{37}\mathrm{Na}$ lie at or very near the neutron drip line in this region. In this work, we report the first $\beta$-decay half-life measurements of $^{31}\mathrm{F}$ and $^{37}\mathrm{Na}$, utilizing the state-of-the-art experimental setup of the FRIB Decay Station Initiator (FDSi).

The reported results represent the shortest $\beta$-decay half-lives measured to date and serve as sensitive benchmarks for theoretical shell-model calculations in the $N = 20\text{--}28$ region. Comparisons with calculations using the sdpf-m [1] and SDPFSDG-MU [2] interactions show overall good agreement within uncertainties associated with the effective interactions and adopted $Q_{\beta}$ values. However, further investigations are ongoing to understand differences between interactions and localized discrepancies with experiment, particularly in relation to the role of cross-shell excitations and intruder configurations.

References
[1] Y. Utsuno et al., Phys. Rev. C 60, 054315 (1999).
[2] S. Yoshida et al., Phys. Rev. C 97, 054321 (2018).

Acknowledgment
This work was supported by the U.S. Department of Energy (DOE) and the National Science Foundation (NSF) under Grant Nos. PHY-1848177 (CAREER) and PHY-2412343.

Speaker: Tawfik Gaballah (Mississippi state university)

3:30 p.m. → 4:00 p.m. Coffee break

4:00 p.m. → 5:30 p.m. Monday Afternoon Late Session: (Chair Kevin Hahn)

4:00 p.m. Beta-decay spectroscopy with laser-polarized beams at CERN ISOLDE

Nuclear spin orientation provides access to an additional observable in beta-decay experiments – the anisotropy of radiation emission, which reflects the parity-nonconserving nature of the weak interaction [1]. The resulting directional distribution of the radiation depends on the asymmetry parameter, which is sensitive to the angular momentum change, as well as on the polarization of the parent nuclei. Higher beam polarization leads to more pronounced anisotropy, which can be used to determine the asymmetry parameter and thereby assign the spins and parities of excited states. Such assignments are particularly straightforward for states involved in allowed Gamow–Teller transitions, as demonstrated in experiments at RIKEN [2, 3] and TRIUMF [4, 5], where beta-decay spectroscopy with polarized nuclei was pioneered.

In this contribution, the CERN ISOLDE’s first beta-decay spectroscopy experiment with laser-polarized beams is presented. A dedicated station has been designed and integrated into the VITO beamline [6]. Full compatibility of the new setup was demonstrated in commissioning campaigns with polarized atoms of 47,49,51K. The new station at VITO opens opportunities to advance beta-decay studies at ISOLDE and to provide new insights into the decay mechanisms of strong beta-delayed neutron emitters [7, 8].

[1] K. S. Krane, In: H. Postma, N. J. Stone, Low Temp. Nucl. Orient., North Holland, 1986.
[2] H. Miyatake et al., Phys. Rev. C 67, 014306 (2003).
[3] H. Ueno et al., Phys. Rev. C 87, 034316 (2013).
[4] Y. Hirayama et al., Physics Letters B 611, 239 (2005).
[5] H. Nishibata et al., Phys. Rev. C 111, 064317 (2025).
[6] M. Kowalska et al., Phys. G: Nucl. Part. Phys. 44, 084005 (2017).
[7] Z. Y. Xu, R. Grzywacz et al., Phys. Rev. Lett. 133, 042501 (2024).
[8] P. Dyszel, R. Grzywacz et al., Phys. Rev. Lett. 135, 152501 (2025).

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Funded by the European Union's HORIZON Programme under the Grant Agreement No. 101212216 (RADESO).

Speaker: Monika Piersa-Siłkowska (University of Tennessee & Universidad Complutense de Madrid)

4:30 p.m. Nuclear structure of $^{114}$Sn via $\beta$ decay of $^{114}$Sb with GRIFFIN

The semi-magic Sn ($Z$ = 50) isotopes with neutron numbers extending from $N$ = 50 to beyond the $N$ = 82 shell, provide an important testing ground for studying the evolution of nucleon–nucleon interactions across the chain. Although ground states of Sn isotopes are predominantly spherical, mid-shell isotopes ($A$ = 112–122) display shape coexistence associated with proton 2p–2h intruder configurations, leading to deformed rotational bands built upon excited 0$^+$ states [1]. Recent studies have suggested different bandheads for these intruder structures, namely 0$^+_2$ state in $^{118}$Sn and the 0$_3^+$ state in $^{116}$Sn [2,3]. This motivates a detailed spectroscopic investigation of the neighboring nucleus $^{114}$Sn to clarify the bandhead of the shape-coexisting structure and to search for possible bands built upon the 0$_3^+$ state. Furthermore, recent theoretical and experimental studies have proposed the presence of pygmy quadrupole resonance (PQR) in $^{112,114,124}$Sn, although its existence is yet to be firmly established [4,5].

We report on a comprehensive $\gamma$-ray spectroscopy study of $^{114}$Sn following the $\beta$ decay of $^{114}$Sb, produced at the TRIUMF–ISAC facility. The resulting $\gamma$ rays were detected using the GRIFFIN spectrometer, consisting of 15 Compton-suppressed HPGe clover detectors with a total of 60 crystals, facilitating angular correlation measurements. Ancillary detectors included the Zero Degree Scintillator (ZDS) for $\beta$ tagging and the PACES array of five Si(Li) detectors for conversion-electron spectroscopy. In addition, eight LaBr$_3$(Ce) detectors were employed for lifetime measurements using fast-timing techniques.

In this work, more than 600 new $\gamma$-ray transitions and over 100 new excited states have been established in $^{114}$Sn. The results confirm the 0$_2^+$ state as the bandhead of deformed 2p-2h band, in contrast to $^{116}$Sn. The implications for the evolution of shape-coexisting structures near the neutron mid-shell and low-lying quadrupole strength in this region will be discussed at the conference.

[1] P. Garrett et al., Prog. Part. Nucl. Phys. 124, 103931 (2022).

[2] K. Ortner et al., Phys. Rev. C 102, 024323 (2020).

[3] J. L. Pore et al., Eur. Phys. J. A 53, 27 (2017).

[4] M. Spieker et al., Phys. Lett. B 752, 102–107 (2016).

[5] N. Tsoneva et al., Nucl. Phys. A 990, 183–198 (2019).

Speaker: Madhu Madhu (Simon Fraser University)

4:50 p.m. Exploring the structure of nuclei with A≈100 via β decay

A sudden ground-state shape transition is known to occur sharply at $N=60$ for several nuclei in the $A\approx\!100$ region [1]. Dramatic changes are observed in the energy spectra of Sr and Zr, including an appearance of low-energy $0^+$ states that are associated to competing configurations characterized by different nuclear shapes. In contrast, in Mo isotopes the ground state shape evolution appears to be more gradual, in accordance with the moderate change in $E_x(2_1^+)$ across $N=60$ [1], proposed to be the result of emerging triaxiality [2].

Recent state-of-the-art Monte Carlo Shell Model (MCSM) calculations [3] reproduced the ground-state band properties throughout the Zr isotopic chain and suggested the appearance of multiple shape coexistence in $^{100}$Zr. In addition, it was proposed that the abrupt shape transition at $N=60$ is caused by an inversion of a spherical and prolate-deformed configurations, corresponding to the ground states of $^{98}$Zr and $^{100}$Zr, respectively, appearing with small to no mixing between them due to type-II shell evolution [3].

To test the MCSM predictions and investigate in detail this fascinating region, a $\beta$-decay study of $A=100$ isotopes was carried out at the TRIUMF-ISAC facility. A radioactive ion beam mixture of $^{100}$Rb and $^{100}$Sr was used and population of excited states in isotopes ranging from $^{100}$Sr to $^{100}$Mo was observed. The powerful GRIFFIN array [4] coupled to a tape station allowed to explore the level structure of several nuclei with a main focus on $^{100}$Zr ($N=60$). In addition, $^{100}$Mo ($N=58$) was studied with the aim of observing low-intensity $\gamma$-ray transitions and establishing spins of excited states that have remained undetermined to date. While a low-energy Coulomb-excitation study [5] revealed that the triaxial ground state of $^{100}$Mo coexists with a prolate-deformed $0_2^+$ level, little is known for the higher-lying $0^+$ states.

Selected results will be highlighted, including the identification of new $0^+$ states in $^{100}$Zr via $\gamma$-$\gamma$ angular correlations and candidates for $2^+$ states built on them. The mixing of coexisting configurations will be addressed relying on high-precision branching and mixing ratios obtained in this work. In addition, a comparison between Zr isotopes with $N=58$,$60$ will be presented, reporting on recent key findings from our group in $^{98}$Zr [6]. Finally, for the first time results concerning newly discovered structures in $^{100}$Mo will be presented and a possible multiple-shape coexistence scenario will be discussed.

[1] P.E. Garrett et al., Prog. Part. Nucl. Phys. 124 (2022) 103931.
[2] R. Rodriguez-Guzman et al., Phys. Lett. B 691, 202 (2010).
[3] T. Togashi et al., Phys. Rev. Lett. 117 (2016) 172502.
[4] A.B. Garnsworthy et al., Nucl. Instrum. Methods Phys. Res., Sect. A, 918 (2019).
[5] K. Wrzosek-Lipska et al., Phys. Rev. C 86, 064305 (2012).
[6] K. Mashtakov et al., in preparation.

Speaker: Desislava Kalaydjieva (University of Guelph)

5:10 p.m. Electrons for Neutrinos: from MAMI to MESA

Next-generation long-baseline neutrino experiments aim to measure neutrino oscillation parameters with percent-level precision and to determine the CP-violating phase in the lepton sector of the Standard Model. Achieving these ambitious goals requires a significantly improved understanding of neutrino–nucleus interaction cross sections, which currently constitute one of the dominant sources of systematic uncertainty. Electron-scattering experiments can provide essential constraints on nuclear response functions through high-statistics and high-precision measurements, since electrons probe the same vector current component involved in neutrino interactions. Such measurements therefore offer a powerful and complementary approach to reducing nuclear-model uncertainties.
In this contribution, recent results from electron-nucleus scattering experiments performed at MAMI will be presented, together with prospects for future studies at the upcoming MESA energy-recovery accelerator facility.

Speaker: Luca Doria (Johannes Gutenberg University Mainz)

6:00 p.m. → 8:00 p.m. Reception

Tue, July 28

9:00 a.m. → 10:30 a.m. Tuesday Morning Early Session: (Chair David Jenkins)

9:00 a.m. Nuclear structure for X-ray burst models via beta decay at FRIB

Type I X-ray bursts are frequent transient events observed in the Milky Way using space-based X-ray telescopes. Each burst results from a thermonuclear explosion on the surface of an accreting neutron star in a close binary system. Along with various astrophysical parameters, X-ray burst models are sensitive to nuclear uncertainties. Among the most significant nuclear uncertainties identified are the thermonuclear rates of the $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne, $^{59}$Cu(p,$\gamma$)$^{60}$Zn, and $^{59}$Cu(p,$\alpha$)$^{56}$Ni reactions. To address these uncertainties, an experimental campaign was recently completed at FRIB using the beta decays of $^{20}$Mg and $^{60}$Ga and the Gaseous Detector with Germanium Tagging II (GADGET II) system. The goals are to measure the alpha-particle branching ratio of the key $^{19}$Ne resonance, and to discover and characterize resonances in $^{60}$Zn by their energies, spins/parities, and branching ratios. Preliminary analysis of these data sets will be presented, along with plans to follow up by measuring $^{60}$Zn resonance lifetimes using $^{60}$Ga decay and the new Lifetimes and Branching Ratios Apparatus (LIBRA) system, also at FRIB.

Speaker: Christopher Wrede (Michigan State University and Facility for Rare Isotope Beams)

9:30 a.m. Probing explosive nucleosynthesis with radioactive beams

Explosive astrophysical environments, such as X-ray bursts, novae and supernovae govern nucleosynthesis on the proton-rich side of the valley of stability. In these sites, nucleosynthesis proceeds mainly through p- and α- induced reactions, as well as photodisintegration reactions that push the nuclear flux away from the valley of stability. Modeling these environments requires detailed knowledge of nuclear properties and reaction rates for the nuclei involved. To address this need, direct measurements in the astrophysically relevant energy region with radioactive beams are essential. In this talk, I will present two radioactive beam experiments for explosive nucleosynthesis.

In the lighter-mass region, I will discuss one of the main breakout pathways from the hotCNO cycle towards explosive burning and the rp process, the $^{14}$O(α,p)$^{17}$F reaction. At typical burst temperatures, this reaction proceeds predominantly through a 6.15 MeV resonant state in $^{18}$Ne, that can decay through p, α or possibly 2p emission. Using the Active Target and Time Projection Chamber (ACTAR TPC) at TRIUMF, the 6.15 MeV resonance was populated through inelastic proton scattering on a radioactive $^{17}$F beam. This measurement aims to provide branching ratios between the 2p, p, and α decay channels by observing all particles in the final state.

Moving on towards the heavy elements and the astrophysical γ process, I will present the first measurement of the $^{73}$As(p,γ)$^{74}$Se reaction, one of the main destruction mechanisms of the lightest p nucleus $^{74}$Se. The measurement was performed using a radioactive $^{73}$As beam with the Summing NaI (SuN) detector at the Facility for Rare Isotope Beams. Along with the total cross-section measurement, the impact of the extracted reaction rate in the production of $^{74}$Se in Type II supernovae will be presented.

Speaker: Artemis Tsantiri (University of Regina)

9:50 a.m. Direct Neutron Capture Measurements with a Storage Ring

Neutron capture reactions are fundamental to understanding the synthesis of elements heavier than iron in stellar environments, occurring through the slow (s), intermediate (i), and rapid (r) neutron‑capture processes. While neutron‑capture cross sections along the valley of stability—particularly for stable or long‑lived isotopes—have been extensively studied, direct measurements on short‑lived nuclides (T₁/₂ ≪ 1 year) remain inaccessible with current techniques.

Heavy‑ion storage rings coupled to radioactive‑beam facilities provide a powerful platform for advancing such studies. Over the past decade, the ESR and CRYRING at GSI Darmstadt have enabled inverse‑kinematics measurements of astrophysically relevant reaction rates, though to date only for charged‑particle reactions. With the NRING project at CRYRING [1], we propose the first facility capable of performing direct neutron‑capture measurements on shorter-lived isotopes.

In this contribution, I will outline the NRING concept and discuss its expected capabilities and limitations. Ultimately, fully harnessing this new approach will require the development of a dedicated future “neutron‑capture storage ring” integrated with an ISOL facility—an advancement that could enable hundreds of direct neutron‑capture measurements on short‑lived nuclei down to half-lives of seconds in the coming decade. One possibility for such a new dedicated facility could be the TRIUMF Storage Ring (TRISR) [2] at the TRIUMF-ISAC facility.

[1] Ariel Tarifeño-Saldivia, César Domingo-Pardo, Iris Dillmann, Yuri A. Litvinov, "Direct Neutron Reactions in Storage Rings Utilizing a Supercompact Cyclotron Neutron Target", [https://arxiv.org/abs/2508.15465], subm. to Phys. Rev. Acc.and Beams (2026)
[2] I. Dillmann, O. Kester, et al., Eur. Phys. J. A59 (2023) 105.

Speaker: Iris Dillmann (TRIUMF)

10:10 a.m. ORRUBA: two decades of discovery

ORRUBA (the Oak Ridge Rutgers University Barrel Array) comprises the largest suite of highly-segmented silicon detectors for radioactive beam physics in the US. It was initially conceived as a standalone ~300-channel detector array for measuring (d,p) reactions on fission fragments around the Coulomb barrier. Initial experiments were performed in 2006, including the first measurement of the 132Sn(d,p)133Sn reaction.

Over the following two decades, ORRUBA has been further developed and expanded (now 1200 channels), with various auxiliary detectors. It has been deployed at numerous facilities (ATLAS, NSCL, FRIB, HIgS, ...) for measurements of direct and compound nuclear reactions spanning a wide range of beam energies and masses, to inform nuclear structure, reactions, astrophysics and applications. Particular mileage has been gained from coupling to other instruments, including the GODDESS coupling to large HPGe arrays (Gammasphere and GRETINA), and coupling to the S800 spectrometer and the JENSA gas-jet target. An overview of some of these experiments, upgrades and results will be presented, with a focus on recent experiments (including the first at FRIB), and a look toward future plans for operation with the SECAR recoil separator and GRETA at FRIB and ATLAS.

Work supported in part by the US DOE Office of Science (NP) under Contracts DE-AC05-00OR22725 (ORNL), DE-AC52-07NA27344 (LLNL), DE-FG02-96ER40963 (UTK), DE-AC02-05CH11231 (LBL), under (NNSA) Contract no. DE-NA0003897 (Rutgers), and the National Science Foundation.

Speaker: Kate Jones (University of Tennessee)

10:30 a.m. → 11:00 a.m. Coffee Break

11:00 a.m. → 12:30 p.m. Tuesday Morning Late Session Block: (Chair: Alan Wuosmaa)

11:00 a.m. Coulomb Breakup and soft E1 excitation of Halo Nuclei

Soft E1 excitation, characterized by enhanced electric dipole strength at low excitation energies, is a distinctive feature of neutron halo nuclei, and has been extensively studied via Coulomb breakup reactions [1,2]. It serves as a powerful spectroscopic probe for both one-neutron and two-neutron halo nuclei. In this talk, we present recent Coulomb breakup studies of the one-neutron halo nucleus 31Ne, and the two-neutron halo nuclei, 19B [3], and 22C, performed with the SAMURAI spectrometer at RIBF, RIKEN. We discuss new insights into the soft E1 excitation, particularly in two-neutron halo nuclei. We also discuss future perspectives for Coulomb breakup studies of halo nuclei.

[1] T. Nakamura, Coulomb breakup and soft E1 excitation of neutron halo nuclei, in Handbook of Nuclear Physics, edited by I. Tanihata, H. Toki, and T. Kajino (Springer Nature Singapore, Singapore, 2020) pp. 1-37
[2] T. Aumann and T. Nakamura, The electric dipole response of exotic nuclei, Physica Scripta 2013, T152, 014012 (2013).
[3] K.J. Cook et al., Phys. Rev. Lett. 124, 212503 (2020).

Speaker: Prof. Takashi Nakamura (Institute of Science Tokyo)

11:30 a.m. First spectroscopic study with direct reactions at RAON

The Rare isotope Accelerator complex for ON-line experiments (RAON) is the first Radioactive Isotope (RI) beam facility in Korea. After the commissioning of the Super-Conducting Linac (SCL3) and the first commissioning experiments carried out in summer 2024, 2025 was marked for the first spectroscopic campaign at RAON, with stable and unstable beams. For this purpose, a large amount of effort was devoted at the Center for Exotic Nuclear Studies (CENS) to develop nuclear detection instruments especially intended for experiments with direct reactions in inverse kinematics: these include ASGARD array of HPGe detectors and STARK Jr silicon barrel array that were the major workhorses of the aforementioned experimental campaign.

This contribution will report on the first spectroscopic study using direct reactions performed at RAON, discussing the physics motivation of these studies, the detailed experimental setup: its current status and the achieved performance, including in-beam commissioning results; and the preliminary outcome of this work. Ongoing development efforts and future experimental plans will also be discussed.

Speaker: Dr Xesus Pereira-Lopez (CENS, IBS)

11:50 a.m. Study of the structure of neutron-rich isotopes 23, 24, 25F in inverse kinematics with the R3B experimental setup at GSI/FAIR

Understanding the structure of nuclei far from stability remains one of the major challenges in nuclear physics. In particular, many-body correlations can lead to nuclear systems whose properties deviate significantly from those expected from a simple independent-particle picture. A striking example is the drastic extension of the neutron drip line for $Z=9$ isotopes compared with $Z=8$ nuclei~[1]. The neutron drip line marks the limit of nuclear binding beyond which additional neutrons cannot be bound to the nucleus and are immediately emitted. Investigating the structure of $Z=8$ and $Z=9$ isotopes through one-nucleon removal reactions is therefore essential for understanding this phenomenon.

In this work, we study the reaction \textsuperscript{25}F(p,2p)\textsuperscript{24}O in inverse kinematics in order to characterize the final states of the residual \textsuperscript{24}O nucleus. This measurement builds upon previous studies~[3], but benefits from the higher resolution, statistics, and acceptance provided by the R\textsuperscript{3}B (Reactions with Relativistic Radioactive Beams) experimental setup at GSI/FAIR.

In the experiment, a cocktail beam containing \textsuperscript{25}F beam at $650$ MeV/nucleon impinges on a $5$ cm long LH\textsubscript{2} target. The outgoing oxygen fragments (\textsuperscript{22,23,24}O) produced in the (p,2p) reaction are measured in coincidence with the reaction products, providing information on the populated ground and excited states of \textsuperscript{24}O. Since \textsuperscript{23}O and \textsuperscript{24}O do not exhibit bound excited states, their de-excitation proceeds through the emission of one or two neutrons. These neutrons are detected with high resolution in the NeuLAND [3] neutron detector, allowing the reconstruction of unbound states in \textsuperscript{24}O and \textsuperscript{23}O. In addition, bound states of \textsuperscript{22}O are studied using the CALIFA calorimeter [4].

The measured cross sections for the population of individual final states, together with the reconstructed momentum distributions of the decaying \textsuperscript{24}O system, will provide valuable information on the configuration of the \textsuperscript{24}O core in \textsuperscript{25}F. Moreover, since our cocktail beam also contains \textsuperscript{23, 24}F, a extension of this study towards \textsuperscript{22, 23}O will allow a complete spectroscopic characterization of both bound and unbound states of \textsuperscript{22, 23, 24}O.

[1] D. S. Ahn et al., Phys. Rev. Lett 123, 212501 (2019). DOI: 10.1103/PhysRevLett.123.212501.

[2] T. L. Tang et al., Phys. Rev. Lett 124, 212502 (2020). DOI: 10.1103/PhysRevLett.124.212502.

[3] K. Boretzky et al., Nuclear Instrum. Methods Phys. Res. A 1014, 165701 (2021). DOI: 10.1016/j.nima.2021.165701.

[4] H. Alvarez-Pol et al., Nuclear Instrum. Methods Phys. Res. A 767, 453 (2014). DOI: 10.1016/j.nima.2014.09.018.

Speaker: Pablo González Rusell (USC (IGFAE))

12:10 p.m. Probing Halo Structure in the 1/2$^{+}$ Excited State of $^{17}$C via Interaction Cross Section Measurements

Halo nuclei have served as benchmarks for understanding weakly-bound and continuum effects on the evolution of single-particle energies and particle correlations at and beyond the dripline. However, direct evidence of halo structures in nuclear excited states has remained elusive due to experimental challenges, thus limiting the number of cases available for investigating halo formation near the threshold.

A new technique, based on a combination of gamma-ray spectroscopy and the transmission method, has been developed to probe the presence or absence of halos in excited states. This novel approach, termed the Gamma-decay Transmission Method, quantifies gamma-ray yields with and without a reaction target to extract the interaction cross section of excited states.

The 1/2$^{+}$ excited state of $^{17}$C, characterized by a small one-neutron separation energy of 0.5 MeV and a significant s-wave component, is a strong halo candidate and therefore well suited to demonstrate the new method. An experimental study using this technique was performed at FRIB utilizing GRETINA, the S800 spectrograph, and a dedicated target assembly to produce $^{17}$C. This talk will describe the new methodology and provide an overview of preliminary results.

Speaker: Andrew Douglas (FRIB/Michigan State University)

12:30 p.m. → 2:00 p.m. Lunch

2:00 p.m. → 3:30 p.m. Tuesday Afternoon Early Session Block: (Chair: Alison Bruce)

2:00 p.m. A universal fate for spin-orbit partners in the weak-binding regime?

The solenoidal-spectrometer technique was pioneered at Argonne just over 15 years ago with the HELIOS spectrometer. Its success has been emulated in Europe at CERN’s HIE-ISOLDE facility with the ISOLDE Solenoidal Spectrometer and at DOE’s Facility for Rare Isotope Beams with SOLARIS. Solenoidal spectrometers are highly versatile tools, perhaps more so than originally imagined, for studying direct reactions in inverse kinematics (mainly with radioactive ion beams) with good resolution. From the solenoidal spectrometer programs at ATLAS, CERN, and FRIB, key insights have emerged: the behavior of single-particle energies in weakly bound nuclei suggests a seemingly ubiquitous way nuclear structure evolves towards the limits of stability. I will present physics highlights from recent measurements that reflect this. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357.

Speaker: Dr Benjamin Kay (Argonne National Laboratory)

2:30 p.m. Abrupt structural transition in exotic molybdenum isotopes unveils an isospin-symmetric island of inversion

Protons and neutrons in nuclei are arranged in orbitals that follow a shell structure, with energy gaps at specific magic numbers. Experiments using radioactive beams have shown that these magic numbers vanish in some neutron-rich isotopes. This results in unusual arrangements, where configurations with nucleons scattered to higher energy orbitals are the most bound, forming what has been called "Islands of Inversion".
We have measured the lifetimes of 2+ states in 84Mo and 86Mo isotopes, discovering a dramatic structural change. This has been understood as the boundary of a "Isospin-Symmetric Island of Inversion" [1], where both proton and neutron excitations play an equal role and evolution of collectivity is governed by three-nucleon forces.

[1] J. Ha, F. Recchia et al. Abrupt structural transition in exotic molybdenum isotopes unveils an isospin-symmetric island of inversion. Nat Commun 16, 10631 (2025).
https://doi.org/10.1038/s41467-025-65621-2

Speaker: Francesco Recchia (University of Padova and INFN)

2:50 p.m. Direct Observation of Superallowed Alpha Decay of 104Te

Historically, the simplest $\alpha$ decay is that of $^{212}$Po, which is conceptualized as a doubly magic $^{208}$Pb core with a valence $\alpha$ particle. For decades, this well-measured isotope has stood as the baseline for $\alpha$-decay models and comparison among other $\alpha$-emitting nuclei. However, a lighter region of $\alpha$ radioactivity was found in neutron-deficient tellurium and xenon isotopes resulting from the Z=50 and N=50 shell closures. Discovered by Macfarlane and Siivola, these decays are enhanced relative to $^{212}$Po, allowing the authors to coin the term “superallowed” $\alpha$ decay for the nuclei [1]. The self-conjugate decay of $^{104}$Te to $^{100}$Sn was then postulated to be the most enhanced $\alpha$ decay due to an increase in proton-neutron correlations. Two events of $^{104}$Te were measured by Auranen et al. Despite limited statistics, the authors placed an upper limit on the half-life via the decay chain of $^{108}$Xe [2]. This work reports an experiment at RIKEN RIBF using the fragmentation of $^{124}$Xe to produce the decay chain of $^{108}$Xe to $^{104}$Te to $^{100}$Sn [3]. In preparation for the short lifetime, a fast-response charged particle detector was utilized [4]. The half-life of $^{104}$Te was measured for the first time and is found to be the fastest ground-state $\alpha$-emitting nucleus known to date. Additionally, the deduced preformation demonstrates that the enhancement is greater for $^{104}$Te than for any other $\alpha$-decaying nucleus [3]. This presentation will compare the results with previous results from Auranen et al and numerous theoretical models.

[1] R. Macfarlane and A. Siivola, Phys. Rev. Lett. 14, 144 (1965)
[2] K. Auranen, et al. Phys. Rev. Lett. 121, 182501 (2018)
[3] I. Cox, et al. Nature, in Press (2026) https://doi.org/10.21203/rs.3.rs-7991707/v1
[4] Y. Xiao, et al. Phys. Rev. C 100, 034315 (2019)

This work was supported by US DOE No. DE-FG02-96ER40983 and NNSA No. DE-NA0003899

Speaker: Ian Cox (Argonne National Laboratory)

3:10 p.m. Fast-Beam One-Neutron Pickup Reactions: A Selective Probe of High-ℓ States

High-$\ell$ single-particle configurations provide critical information on nuclear structure and place important constraints on theoretical models but are typically difficult to access experimentally due to their weak population in commonly used experimental methods such as low-energy transfer and knockout reactions. Intermediate-energy one-neutron pickup reactions in inverse kinematics are uniquely suited to this problem as due to poor angular momentum matching the population of high-$\ell$ ($\ell$ $\geq$3) states are drastically enhanced whilst also suppressing low-$\ell$ transfer [1,2]. When applied to nuclei with high-lying high-$\ell$ orbitals these reactions provide selective access to states that have remained unobserved in previous $\gamma$-ray spectroscopy studies, even in otherwise well-studied systems.
Here, one-neutron pickup reaction experiments performed at the former NSCL will be discussed. Beams delivered by the Coupled Cyclotron Facility were impinged on a $^{12}$C target to induce one-neutron pickup reactions. Prompt $\gamma$ rays were detected with the Gamma-Ray Energy in-beam Nuclear Array (GRETINA), while reaction residues were subsequently identified in the S800 magnetic spectrometer. These measurements build on earlier one-neutron pickup studies performed at the NSCL which first demonstrated the strong selectivity of one-neutron pickup reactions [3,4]. Results from the $^{12}$C($^{46}$Ca,$^{47}$Ca+ $\gamma$)X reaction will be discussed, which provided new insight into the placement and strength of the ν(0f$_{5/2}$) and ν(0g$_{9/2}$) orbitals in $^{47}$Ca [5], including the population of states not previously observed in $\gamma$-ray spectroscopy. In addition, preliminary results from the ongoing analysis of the $^{12}$C($^{44}$Ar,$^{45}$Ar+$\gamma$)X reaction will be presented, further demonstrating the strong selectivity of one-neutron pickup reactions and their potential to probe high-$\ell$ structure in neutron-rich nuclei.

[1] D. Brink, Phys. Lett. B 40, 37 (1972)
[2] W. R. Phillips, Rep. Prog. Phys. 40, 345 (1977)
[3] A. Gade, J. A. Tostevin et al, Phys. Rev. C 93, 031601 (2016)
[4] A. Gade, J. A. Tostevin et al, Phys. Rev. C 93, 054315 (2016)
[5] T. Parry, A. Gade, B. A. Brown et al, Phys. Rev. C 112, 014328 (2026)

Speaker: Thomas Parry (Facility for Rare Isotope Beams)

3:30 p.m. → 4:00 p.m. Coffee Break

4:00 p.m. → 5:30 p.m. Tuesday Afternoon Late Session Block: (Chair: Greg Lane)

4:00 p.m. The Gamma Ray Energy Tracking Array - GRETA

The Gamma-Ray Energy Tracking Array (GRETA) Project started in 2017, following nearly a decade of successful science with the predecessor GRETINA array. Led by LBNL, with a team including partner institutions ANL, ORNL and FRIB, GRETA marked the completion of construction and initial commissioning of all technical systems (mechanical, electronics and computing) with a subset of Quad Detector modules in late summer of 2025. It is currently being installed at the Facility for Rare Isotope Beams (FRIB), with a full array of 30 Quad modules for the first time covering 80% of the 4$\pi$ solid angle. First PAC-approved science measurements are expected in early 2027. I will discuss physics highlights from the decade of GRETINA operations, and review the GRETA project, both scientific and technical aspects, and the progression toward anticipated first science at FRIB.

Speaker: Heather Crawford (Lawrence Berkeley National Laboratory)

4:30 p.m. Recent results on the double-gamma decay

The nuclear two-photon or double-gamma (2γ) decay is a second-order electromagnetic decay process whereby a nucleus in an excited state emits two gamma rays simultaneously. Compared to first-order decay pathways, such as single photon emission or internal electron conversion, the two-photon decay rate is very small. Ideal cases for this search are $0^+ \rightarrow 0^+$ transition where single photon emission is prohibited. However, the only cases where the 2γ decay from a first-excited 0+ state was successfully observed using γ-ray spectroscopy are $^{16}$O, $^{40}$Ca and $^{90}$Zr [1, 2], where the high energy of the transitions is favorable for the 2γ branch. More recently, also the competitive 2γ decay was observed from the long-lived 11/2$^-$ isomer in $^{137}$Ba [3].

For lower decay energies the 2γ branch becomes prohibitively small to be observed in γ-ray spectroscopy (<10$^{-6}$). We have therefore combined the isochronous mode of the Experimental Storage Ring (ESR) at GSI with Schottky resonant cavities. This newly developed Schottky plus Isochronous Mass Spectrometry (S+IMS) allows to study exotic decays of short-lived nuclear states. The obtained mass resolving power enables experiments on nuclear isomers with excitation energies down to ∼100 keV and half-lives as short as a few ms. The first measurement of the partial half-life for the isolated 2γ decay of the 0$^+$ isomer in $^{72}$Ge turned out to be surprisingly short [4]. Recent results for the 2γ decay of the 0$^+$ isomers in $^{98}$Zr and $^{98}$Mo will be presented as well as first steps to measure the weak 2γ branch in $^{72}$Ge by direct γ-ray spectroscopy.

[1] J. Schirmer J. Schirmer, D. Habs, R. Kroth, N. Kwong, D. Schwalm, and M. Zirnbauer, {Double gamma decay in 40Ca and 90Zr, Phys. Rev. Lett. 53, 1897–1900 (1984).
[2] J. Kramp, D. Habs, R. Kroth, M. Music, J. Schirmer, D. Schwalm, and C. Broude, Nuclear two-photon decay in 0+ → 0+ transitions, Nuclear Physics A 474, 412–450 (1987).
[3] C. Walz, H. Scheit, N. Pietralla, T. Aumann, R. Lefol, and V. Yu. Ponomarev, Observation of the competitive double-gamma nuclear decay, Nature 526, 406-409, (2015).
[4] D. Freire-Fernández, W. Korten, Y. Litvinov et al., Measurement of the Isolated Nuclear Two-Photon Decay in 72Ge, Phys. Rev. Lett. 133, 022502 (2024) and https://arxiv.org/pdf/2312.11313.

The main results are based on the experiments E143 and G22-00018, which were performed at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt (Germany) in the context of FAIR Phase-0. This work was supported by the Slovenian Research and Innovation Agency under Grants No. I0-E005 and No. P1-0102, by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (ERC-AdG NECTAR, grant agreement No 884715; ERC-CoG ASTRUm, grant agreement No 68284), by the State of Hesse (Germany) within the Research Cluster ELEMENTS (Project ID 500/10.006), by the STFC (UK), by the NSF grant PHY-2110365, by the BMBF under grant NuSTAR.DA 05P19RDFN1, by the JSPS KAKENHI Grant Number T23KK0055. Work at ANL is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract No. DE-AC02-06CH11357.

Speaker: Michael Weinert

4:50 p.m. Neutron spectroscopy at the FRIB Decay Station Initiator

The FRIB Decay Station Initiator [All25] was designed for comprehensive decay studies, including the ability to perform beta-delayed neutron emission studies. The bn-precursors investigated so far with FDSi range from doubly magic 24O to deformed 111Nb. The analysis of three cases was recently completed at the University of Tennessee. The measurement of 24O reveals the role of continuum coupling in neutron emission [Neu26] by directly measuring the widths of nuclear resonances populated in beta decay. The decay of deformed 44S revealed an unexpected suppression of the L=0 neutron emission channel, and we are investigating the nature of this process using microscopic models [Bra26]. Finally, the decay of 54K to doubly magic 54Ca demonstrated a role of two-body currents [Gys18] in very neutron-rich nuclei [Xu26]. These experimental results show that beta-delayed neutron emission is an effective tool for studying very neutron-rich nuclei and provide new insights into these exotic nuclei.

This research was sponsored by the U.S. Department of
Energy, Office of Science, Office of Nuclear Physics under DE-FG02-96ER40983, and by the Stewardship Science Academic Alliances program through DOE Award No. DE-NA0003899.

[All25] J.M. Allmond and R. Grzywacz, Nuclear Physics News 35, 24 (2025).
[Bra26] N. Braukman et al. to be submitted
[Gys18] P. Gysbers et al., Nature Physics 15, 428 (2019)
[Neu26] S. Neupane et al. submitted
[Xu26] Z. Xu et al. submitted

Speaker: Robert Grzywacz (University of Tennessee)

5:10 p.m. Study of shape coexistence and triaxial deformation in 56Cr using AGATA spectrometer: The puzzling B(E2) values

The Cr isotopes with N≥28 are a good testing ground for rapid shape evolution from a spherical to a well deformed region close to N=40 [1]. Among the Cr isotopic chain, the $^{56}$Cr (N=32) shows a very particular interest. The appearance of a subshell closure in this nucleus is indicated by high excitation energy of the 2$^+_1$ state and reduced B(E2:2$^+_1\rightarrow$0$^+_1$) values [2] compared to neighbouring Cr isotopes, same as in $^{52}$Ca and $^{54}$Ti [3] nuclei. Shell-model calculations, using various interactions and/or effective charges, are able to reproduce well the trend of the energy of the 2$^+_1$ state along the Cr isotopic chain but fail to reproduce the staggering of the B(E2:2$^+_1\rightarrow$0$^+_1$) values with a minimum at $^{56}$Cr (N=32) [1]. Beyond mean-field calculations using Gogny interaction reproduce the experimental zigzag behaviour in the Ti isotopes without any need to invoke effective charges but again this is not the case for the Cr isotopes [4]. Calculations performed with the AMD+HFB framework [5] aiming to investigate the triaxial deformation of the states and shape coexistence in this region reproduce the staggering of B(E2) values at N=32 but the theoretical values of B(E2) remain much higher than the experimental ones [6].

To get an insight into the structure $^{56}$Cr, shape coexistence and triaxial deformation were studied in a recent experiment via lifetime measurements of the 0$^2_+$ and 2$^2_+$ states employing the RDDS and the DSAM technique. The states of interest were populated using a two-neutron transfer reaction: $^{54}$Cr($^{18}$O,$^{16}$O)$^{56}$Cr. Gamma rays were measured using the state of the art of gamma-ray spectroscopy, the AGATA array [7], coupled with the SPIDER silicon detector [8] to reach the needed channel selectivity. Experimental results will be discussed and compared to theoretical calculations.

[1] M. Seidlitz et al., Phys. Rev C 84, 034318 (2011).
[2] A. Burger et al., Physics Letters B 622 (2005) 29–34. ̈
[3] R.V.F. Janssens et al., Physics Letters B 546 (2002) 55–62.
[4] T.R. Rodriguez and J. Luis Edigo, PRL 99, 062501 (2007).
[5] Y. Kanada-En’yo et al., C.R. Physique 4 (2003) 497-520
[6] M. Kimura, Presentation at TNP meeting.
[7] J. J. Valiente Dobón et al., Nuc. Instr. and Meth. A 1049 (2023) 168040
[8] M. Rocchini et al., Nucl. Instr. and Meth. A 971 (2020) 164030

Speaker: Julgen Pellumaj (INFN-Padova, University of Padova)

5:30 p.m. → 6:00 p.m. Break

6:00 p.m. → 8:00 p.m. Poster Session: Posters

Convener: Krzysztof Starosta (SFU)

6:00 p.m. Beta-delayed spectroscopy at the proton drip line with RCMP at TRIUMF

Nuclear $\beta$-decay is a simple and selective approach to populate excited states and obtain precise spectroscopic information. If the imbalance between proton and neutron number is large, levels in the daughter nucleus can be populated above the proton (or $\alpha$) separation energy, leading to single or multi-particle emission. These decay channels provide an opportunity to study nuclear structure at high excitation energy [1], correlation of multi-particle emission, nuclear astrophysics processes [2] and fundamental symmetries.

Detecting the particles emitted after $\beta$-decay with a high efficiency becomes necessary to obtain the full decay path information. The Regina Cube for Multiple Particles (RCMP), a new ancillary detector for the GRIFFIN HPGe $\gamma$-ray spectrometer at TRIUMF [3], was developed in this context, to explore $\beta$-decay at the proton drip line. RCMP is a set of six double-sided silicon strip detectors (DSSD) arranged in a cubic geometry, allowing to measure the energy of charged particles emitted after $\beta$-decay. Added to GRIFFIN, this state-of-the-art setup is the most efficient to date in order to perform this type of study.

RCMP was commissioned at TRIUMF-ISAC, where beams of $^{20}$Mg and $^{21}$Mg were produced with the highest statistical yield measured to date. Corrections such as energy add-back, cross-talk and energy loss have to be taken into account to retrieve the correct physical quantities. This work presents a study of these correction factors and how they affect the obtained results for $^{21}$Mg $\beta$-delayed proton emission. My co-worker, Sydney Plante, will continue by presenting the analysis of the $^{20}$Mg $\beta$-delayed spectroscopy.

[1] M.V. Lund et al. "Systematic trends in beta-delayed particle emitting nuclei: The case of $\beta$p$\alpha$ emission from $^{21}$Mg" Phys. Lett. B 750 (2015)

[2] M.V. Lund et al. "Beta-delayed proton emission from $^{20}$Mg" Eur. Phys. J. A 52.10 (2016)

[3] A.B. Garnsworthy et al. "The GRIFFIN facility for Decay-Spectroscopy studies at TRIUMF-ISAC" Nucl. Instrum. Methods Phys. Res., Sect. A 918 (2019)

Speaker: Emile Cantacuzene (University of Regina)

6:01 p.m. Chiral doublet bands in $^{110,112}$Rh

High spin states of $^{110}$Rh have been reinvestigated by analyzing the high statistics γ-γ-γ and γ-γ-γ-γ coincidence data from the spontaneous fission of $^{252}$Cf using Gammasphere. A partner band with linking transition to the existing yrast band has been observed. Spins and parities are tentatively assigned according to the systematic comparison. Theoretical calculations have been performed to study the possible chiral doublet band structure in $^{110,112}$Rh.

Speaker: Enhong Wang (Shandong University)

6:02 p.m. The Refined Bohr-Mottelson Model for the Description of Collective Motion in Atomic Nuclei

A nuclear system consisting of $A$ nucleons is described in terms of $3A$ independent coordinates. Three coordinates are used in the transformation to the centre of mass frame, three Euler angles are used to set the nucleus in the body-fixed frame, and three variables $\rho$, $\beta$, and $\gamma$ define the size, orientation, and shape of the nuclear inertial ellipsoid. The remaining $3A-9$ coordinates are generalized Euler angles characterizing the internal nucleon motion. A microscopic derivation of the kinetic energy of a nucleus is carried out from first principles resulting in expressions of the kinetic energy contributions from vibrations, rotations, intrinsic motion, and the Coriolis coupling (see also [1]). The derived rotational energy operator depends on the hydrodynamic moments of inertia and the angular momentum operators along the body-fixed axes, which arise naturally from the derivation procedure.

Additionally, the Refined Bohr-Mottelson (RBM) model is introduced, proposing an adjustment to the definition of the nuclear surface of the Bohr-Mottelson model. This redefinition takes into account the constant density of the incompressible nucleus and, by construction, conserves the volume of the nucleus with arbitrary deformation. The obtained collective Hamiltonian is a sum of the monopole and quadrupole Hamiltonians. For small deformations ($\beta\ll 1$) the latter coincides with the Bohr Hamiltonian. We established the relation of our refined deformation parameter $\beta_r$, which ensures constant nuclear volume at arbitrary deformation, with the conventional parameter $\beta$.

The derivations and results will be presented and discussed.

[1] A.Ya.Dzyublik, K.Starosta, Z.Yu, and T.Koike, Phys. Rev. C 110, 014325 (2024).

Speaker: Helena Lo (Simon Fraser University)

6:03 p.m. Development and characterization of SCIGA for direct reaction experiments at RAON

Direct reaction experiments in inverse kinematics are one of the best suited tools to probe a broad range of nuclear properties, providing great insight into the nuclear structure of exotic nuclei. However, the inverse kinematics approach impose constraints in the experimental detection systems: charged-particles are emitted over a large angular range, hence large solid angular coverage is required. In addition, beam intensity limitations for most exotic beams are often compensated with the use of thicker targets at the expense of the excitation energy resolution derived from charged-particles. Measuring gamma-rays in coincidence will much improve the excitation energy resolution, enabling direct reaction studies for nuclei where the level density is too high to distinguish excited states with charged-particles alone.

A large amount of effort was devoted at the Center for Exotic Nuclear Studies (CENS) to develop nuclear detection instruments especially intended for experiments with direct reactions in inverse kinematics at RAON. With the aforementioned constraints in mind, SCIGA (Silicon-CsI-GAGG Array) was designed as a large solid angle array of Silicon-CsI telescopes for charged-particle detection and an array of GAGG scintillator crystals for highly efficient observation of gamma-rays in coincidence. The GAGG crystals provide better resolution than NaI crystals while offering higher intrinsic efficiency than HPGe detectors and more flexibility due to the lack of cooling. SCIGA modular design allows to be used with self-supporting targets or gas cell targets.

This contribution will present SCIGA detailed specifications, performance and current status, including preliminary in-beam commissioning results. Ongoing development efforts and upcoming SCIGA experiments will also be discussed.

Speaker: Dr Xesus Pereira-Lopez (CENS, IBS)

6:04 p.m. Investigating the boundaries of enhanced octupole collectivity in the rare-earth region

Atomic nuclei which exhibit a reflection-asymmetric shape are of considerable interest for the understanding of nuclear structure. These "pear-shaped" nuclei are expected to occur in the regions of the nuclear chart where the octupole degree of freedom is enhanced. Strong octupole correlations manifest when the Fermi surface lies close to single-particle orbitals with quantum numbers $[l,j]$ and $[l-3,j-3]$ giving rise to the octupole magic numbers $N,Z=34,56,88$ and $N=134$. Atomic nuclei in these regions can exhibit enhanced particle-hole interactions from the octupole component of the nucleon-nucleon interaction. The electric-octupole (E3) transition rate provides the most unambiguous signature of octupole collectivity, however such measurements are often extremely challenging as E3 transitions compete very weakly against other allowed transitions.

The region around $Z=56, N=88$ possesses the most complete set of B(E3) values across the nuclear chart with the largest values observed in $^{148,150}$Gd however spectroscopic data for the dysprosium isotopes is largely missing. Within the N=82 chain, increasing B(E3) strength is observed with increasing proton number from $^{136}$Xe (Z=54) to $^{146}$Gd (Z=64) however it remains unknown whether this trend continues at $^{148}$Dy (Z=66) and beyond.

To investigate whether enhanced octupole collectivity is present in dysprosium isotopes and extend or constrain the boundaries of enhanced octupole collectivity, we performed a direct measurement of the B(E3) value in 148-Dy. A beta-decay study of $^{148}$Ho was performed at the TRIUMF facility using the GRIFFIN spectrometer. The mean lifetime of the 3$^-$ state was measured using fast-timing methods with LaBr detectors and the absolute $\gamma$-ray branching ratio of the $3^-\rightarrow0^+$ was obtained enabling a direct measurement of the $B(E3;3_1^-\rightarrow0_1^+)$ value.

Speaker: Pietro Spagnoletti (University of Liverpool)

6:05 p.m. Octopi: A Portable Versatile Gamma-ray Spectrometer

Studies to probe the internal structure and interactions of nuclei often require precise measurement of radiation emitted from nuclear reactions or decay. Any particular modern nuclear experiment requires unique experimental conditions, creating a demand for versatile radiation detection arrays that can meet a wide variety of experimental needs, with minimal adjustment of physical hardware. The Octopi system, designed and implemented at Simon Fraser University (SFU), provides a digital data acquisition system for up to eight Compton-suppressed high-purity germanium gamma-ray detectors and up to four auxiliary detector channels. Real-time event filtering by a user-controlled logic module enables raw signals from detector subsystems to be accepted or rejected based on user-selectable coincidence logic. All triggering parameters are also computer-controlled for versatility. A subsection of the system was recently deployed at TRIUMF to measure muon-induced fission probabilities of U-238. In the near term, the Octopi array will be used at SFU’s Nuclear Science Laboratory for measuring meta-stable radioisotopes produced on a D-T neutron generator.

Speaker: Alex Woinoski

6:06 p.m. FIMP: A Novel Active Implanter for Decay Spectroscopy

Decay spectroscopy at DESPEC requires an active implanter for reliable implantation–decay correlations under cocktail-beam conditions, at high rates, over a large dynamic range, and in strong background conditions. In the current DESPEC setup, AIDA serves as the workhorse implanter, but its decay-event time resolution exceeds 1 μs, and its implantation/decay-pair efficiency in real experiments is typically 25–35%, which limits fast-timing applications. To address this, the Fibre IMPlanter (FIMP) is being developed as a scintillator-based alternative to conventional DSSSD implant detectors.

FIMP is based on orthogonal layers of 0.5 × 0.5 mm² scintillating fibres read out by SiPMs, forming a highly segmented three-dimensional active volume with 2 × 2 × 2 mm³ voxels. Its key novelty is the combination of active stopping, fine 3D segmentation, timing information relevant for implantation–decay correlation studies, and the possibility of charged-particle tracking of implanted ions, β particles, α particles, and secondary fragments. This is particularly attractive for complex cocktail beams, where high granularity and tracking can support isotope identification, background suppression, and improved correlation efficiency. For this geometry, the single-layer detection threshold is of the order of 100 keV, while the effective voxel size is expected to be about 3–4 mm for 1 MeV β particles.

Prototype studies, simulations, and in-beam tests in 2024 and 2025 validated the active-stopping concept, demonstrated detector response to heavy fragments and correlated β/α signals, and guided the next detector iteration. In the July 2025 test, FIMP was operated with fragments ranging from 132Sn to 225Th in four settings, with stable detector performance under beam conditions. Current development is focused on improving detector sensitivity and reducing the β-detection threshold. FIMP thus represents a realistic active implanter for future fast decay-spectroscopy experiments at DESPEC/FAIR.

Speaker: Jelena Vesic (Jozef Stefan Institute, Ljubljana, Slovenia)

6:07 p.m. Rare decay branches of A ~ 90 isomers studied with GRIFFIN using local source production

Modern HPGe detector arrays such as GRIFFIN and TIGRESS at TRIUMF/ISAC allow for extremely high precision $\gamma$-ray branching ratio measurements - as low as $10^{-7}$ depending on counting rate and measurement time - allowing for examination of rare decay branches. A promising avenue for pursuing these high precision measurements at TRIUMF is local production of high activity sources using the TR13 medical cyclotron, located within walking distance of both ISAC halls. We have initiated a series of experiments to study the rare decays of $^{93m}$Mo ($t_{1/2} = 6.85$ hr) and $^{92m}$Nb ($t_{1/2} = 10.15$ d) using MBq activity sources produced on the TR13 via proton bombardment of niobium foils.

For $^{93m}$Mo, our goal is to measure the rare $21/2^+_1 \rightarrow 9/2^+_1$ $E6$ (electric hexacontatetrapole) IT decay branch. Only one $E6$ decay branch has been previously observed, from $^{53m}$Fe decay [1,2]. Despite the presence of significant summing and time-random background, there is some preliminary evidence of this extremely rare decay branch in our data. Additional data will be collected throughout 2026, to improve statistics and evaluate systematic uncertainties.

We have also obtained high statistics $^{92m}$Nb $\rightarrow$ $^{92}$Zr decay data, allowing measurement of the $B(E2; 2^+_2 \rightarrow 0^+_2)$ value in $^{92}$Zr for the first time, as well as improved limits for other weak transitions. These are important indicators as to whether $^{92}$Zr exhibits shape coexistence similar to $^{94}$Zr and other neutron rich zirconiums. We are also searching for direct population of $0^+$ states in $^{92}$Zr in order to definitively assign the spin of the $^{92m}$Nb parent, which may be relevant to the survival of $^{92}$Nb in astrophysical scenarios. The current status of our data analysis and future prospects for local source production experiments at TRIUMF will be discussed.

[1] J. N. Black et al., Physical Review Letters 26 451-454 (1971).
[2] T. Palazzo et al., Physical Review Letters 130 122503 (2023).

Speaker: Jonathan Williams (TRIUMF)

6:08 p.m. High-spin intruder structures in 32Si and 29Al

In $sd$ shell nuclides near the N=20 'island of inversion', shell evolution is indicated by the energies of negative parity states which primarily arise due to single neutron excitation to the higher lying $fp$ orbitals. These intruder states often have high spin (due to the participation of the $0f_{7/2}$ orbital) and can therefore be preferentially populated using fusion-evaporation reactions. Nuclear isomerism can also occur when these intruder states are at similar energies to positive parity states of similar spin.

We have investigated the high spin structures of $^{32}$Si (N=18) and $^{29}$Al (N=16) using $^{12}$C + $^{22}$Ne fusion evaporation reactions at TRIUMF/ISAC-II, with the TIGRESS clover array and a spherical CsI(Tl) array used for gamma ray and charged particle detection/identification, respectively. In $^{32}$Si, the properties of both the yrast $4^+$ state and a $5^-$ isomer resulting from neutron cross-shell excitation have been disputed [1, 2]. We investigated these and other high-spin states, placing the $5^-$ isomer at 5504.88(13) keV and identifying the $4^+$ state at higher energy [3]. A comparison to shell model calculations suggests that this inverted ordering of yrast states is influenced by the Z=14 subshell closure. Several newly observed high-spin states and accompanying transitions were also identified. In $^{29}$Al, we have identified several new negative parity states, including a rotor-like band based on the first $7/2^-$ state [4]. Our future plans in this region will also be discussed, including on-going side channel analysis and an upcoming experiment to study intruder states in $^{34}$Si.

[1] B. Fornal et al. Physical Review C 55 762 (1997).
[2] M. Asai et al. JAERI Tandem Annual Report 2001, 23-24.
[3] J. Williams et al. Physical Review C 108 L051305 (2023).
[4] J. Williams et al. Physical Review C 112 014318 (2025).

Speaker: Jonathan Williams (TRIUMF)

6:09 p.m. The N=126 Factory at Argonne National Laboratory's ATLAS Facility

Precision nuclear data, including nuclear masses, neutron capture cross sections, and $\beta$-decay half lives, are needed throughout the $r$-process path in order to properly model nucleosynthetic pathways. One key region of the nuclear landscape which remains relatively unexplored is neutron rich nuclei surrounding the $N=126$ shell closure. This is due to the difficulty in producing these nuclei using conventional methods such as fragmentation reactions or fission. Multi-nucleon transfer (MNT) reactions between two heavy ions provide an alternate method for producing nuclei near the $N=126$ shell closure with relatively large reaction cross sections.

At Argonne National Laboratory, the N=126 Factory is being developed to employ MNT reactions to produce these neutron rich nuclei near the $N=126$ shell closure. At the N=126 Factory, MNT products are captured in a large volume gas catcher and converted into a low energy beam, which is then accelerated through a dipole separator magnet ($R\sim 10^3$), cooled and bunched, and finally tuned through an MR-TOF system ($R\sim 10^5$). The result is an isotopically pure bunched beam which can be directed towards experimental substations including the CPT high-precision mass spectrometer, a new laser spectroscopy setup, and the RACCOONS decay station. In this presentation I will give an overview of the N=126 Factory and discuss the ongoing commissioning of the facility.

This work is supported in part by the U.S. Department of Energy Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357; by NSERC (Canada), Application No. SAPPJ-2018-00028; by the Nuclear Science Foundation under Grant No. PHY-2310059; by the University of Notre Dame; and with resources of ANL's ATLAS facility, an Office of Science User Facility.

Speaker: Matthew Martin (Argonne National Laboratory)

6:10 p.m. Direct measurement of single-neutron strength of 12C up to 22 MeV using the 11C(d,p) reaction.

The single-nucleon energy levels and configurations of 12C are fundamental to our understanding of nuclear structure, yet they remain primarily defined by theoretical models and parameters extrapolated from neighboring systems. As a semi-closed shell nucleus featuring complex α-cluster states, direct measurements of the excited single-particle configurations in 12C are essential for refining nuclear models and informing nucleosynthesis pathways in astrophysics. We report on the first direct measurement of single-neutron strength in 12C for states up to Ex ≈ 22 MeV. The experiment was performed in inverse kinematics using the 11C(d,p) reaction at 10 MeV/u with the HELIOS spectrometer at Argonne National Laboratory. This setup allowed for high-resolution particle spectroscopy of the ejected protons, enabling the extraction of spectroscopic factors and orbital angular momentum transfers. The experimental configuration, data analysis methodology, and preliminary results regarding the distribution of single-neutron strength are presented.

This work was supported by the National Science Foundation under Grant No. PHY-2012522. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 (ANL) and DE-SC0014552 (UCONN). This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.

Speaker: Tsz Leung Tang (Argonne National Laboratory)

6:11 p.m. Re-emergence of identical bands phenomenon at normal deformation

The rare-earth nuclei around N ~ 90 and A ~ 160 continue to present fascinating as well as challenging physics issues spanning a wide range of angular momenta. Among the many exotic phenomena characterizing nuclei in this mass region, the identical band (IB) phenomenon became a topic of intense research and discussion in the nineties. It was first identified in excited superdeformed (SD) bands of $^{150}$Gd and $^{151}$Tb [1]. Thereafter, many low-spin IBs were also reported both at intermediate (ID) and normal deformation (ND) [2]. However, further exploration of this surprising phenomenon was hindered by the lack of a global explanation valid across the entire periodic chart for all values of deformation.

The subject of “identical high-$K$ bands” at normal deformation in isotopes of a particular isotopic chain has never been investigated through dedicated measurements or theory. Following a recent measurement using a alpha beam and a moderate-size array of eleven Compton-suppressed clover HPGe detectors plus one LEPS (INGA) at the Variable Energy Cyclotron Centre (VECC), Kolkata, India, a new high-$K$ band structure was identified in the $^{162}$Er nucleus (the first-ever) above its $K^\pi=7^-$ isomer [3]. The remarkable similarity between this two-quasiproton structure and the corresponding excitation in $^{164}$Er up to the highest observed spin is intriguing [3]. Further, this finding, when discussed in combination with the two-quasiproton $K^\pi=6^+$ identical high-$K$ bands in $^{174}$Hf and $^{178}$Hf (first recognized in the present work using data from the literature), extends the observation of this phenomenon at ND in pairs of even-even nuclei in the Er and Hf isotopic chains. However, when comparing the properties of the IBs in these two isotopic pairs, it must be concluded that proposed earlier explanations in terms of a delicate cancellation between changes in deformation and pairing do not hold for the Er isotopes [3].

Hence, the present observations call for further experimental and theoretical work. On the one hand, it is important to rule out that the identicality in the present instances is accidental by searching for additional cases, while, on the other, pursue further efforts to develop a single theoretical framework able to account for the occurrence of IBs at all deformations (ND, ID and SD) across the nuclear chart.

The INGA collaboration is gratefully acknowledged. A. C. and S. M. acknowledge the financial assistance received from DAE-BRNS, Govt. of India (Project Sanction No. 37(3)/14/17/2016-BRNS). This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Grant DE-FG02-97ER41041 (UNC), and DEFG02-97ER41033 (TUNL).

[1] T. Byrski et al., Phys. Rev. Lett. 64, 1650 (1990).
[2] C. Baktash, B. Haas, and W. Nazarewicz, Annu. Rev. Nucl. Part. Sci. 45, 485 (1995).
[3] P. K. Nayak et al., under review in Phys. Rev. C.

Speaker: Pramod Kumar Nayak (Bhabha Atomic Research Centre, Mumbai 400085, India & Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India)

6:12 p.m. Study of shape coexistence in Sr-96 via Coulomb excitation experiment

In recent years, shape coexistence in atomic nuclei has been recognized as ubiquitous across the nuclear chart [1]. The structure of nuclei exhibiting shape coexistence reflects an intriguing interplay between microscopic and macroscopic nuclear effects, the understanding of which is one of the greatest challenges of modern nuclear theory. This interplay manifests in the $A\approx100$ region with neutron number N=60, with the Sr and Zr isotopes exhibiting the most rapid onset of ground-state deformation observed across the nuclear landscape. In this context, $^{96}Sr$ represents a transitional nucleus located at the precipice of the region of deformed ground-state shapes. From a structural point of view, the observed sudden onset of deformation can be explained by an inversion of coexisting regular and “intruder” configurations (multiparticle-multihole excitations) where the former possesses a spherical shape, and the latter is deformed. This interpretation is supported both by theoretical calculations [2,3,4] and experimental data for Sr [5,6]. Notably, the $\gamma$-ray decay transition probabilities of the $2^+_1$ state in $^{96}Sr$ and the $2^+_2$ state in $^{98}Sr$, and the spectroscopic quadrupole moments of these states measured in a Coulomb-excitation study [5,6], were found to be consistent with the $0^+_1(^{96}Sr)\leftrightarrow 0^+_2(^{98}Sr)$ inversion scenario. On the contrary, there is still lack of experimental evidence for the correspondence of the low-lying $0^{+}$ states in $^{96}Sr$ to the ground-state configuration $0^+_1$ of $^{98}Sr$. A neutron-transfer reaction was performed at TRIUMF [7] and spectroscopic factors were measured for the excited $0^{+}$ states. Combining these results with the extremely large $\rho^2(E0;0^+_3\rightarrow 0^+_2)$ value of 160(40) [8] led to a suggestion of triple shape coexistence occurring in $^{96}Sr$, with a weakly deformed ground state and two excited $0^{+}$configurations: a deformed and a spherical one, which undergo strong mixing.
Our new experimental study of $^{96}Sr$ aims to shed light on the inversion scenario via the measurement of transition probabilities in a Coulomb excitation experiment performed at TRIUMF. The $^{96}Sr$ radioactive ion beam was produced and delivered by the ISAC-II facility. The $\gamma$ rays from Coulomb-excited states in $^{96}Sr$ were detected by the TIGRESS spectrometer [9], while the scattered beam ions were detected by the S3 detector of the BAMBINO array [10]. An increase of two orders of magnitude in the statistics of the $2_{1}^{+}\rightarrow0^{+}_{1}$ transition was achieved compared to the previous Coulomb-excitation experiment performed at ISOLDE [5,6]. The population of several states in $^{96}Sr$ was observed, including the $4_{1}^{+}$, $0_{2}^{+}$ and $3_{1}^{-}$ ones. Finally, our Coulomb-excitation experiment provided as well high-quality data on $^{96}Y$, allowing a distinction to be made between single-particle and core-coupled states.
Preliminary results of the ongoing data analysis will be presented.

[1] K. Heyde and J.L. Wood, Rev. Mod. Phys. 83, 1467 (2011).
[2] T. Togashi et al., Phys. Rev. Lett. 117, 172502 (2016).
[3] N. Gavrielov et al., Phys. Rev. C. 105, 014305 (2022).
[4] J.E. García-Ramos et al., Phys. Rev. C. 102, 054333 (2020).
[5] E. Clément et al., Phys. Rev. Lett. 116, 022701 (2016).
[6] E. Clément et al., Phys. Rev. C 94, 054326 (2016).
[7] S. Cruz et al., Phys. Lett. B 786, 62 (2018).
[8] T. Kibédi et al., Prog. Part. and Nucl. Phys. 123, 103930 (2022).
[9] G. Hackman and C. E. Svensson, Hyperfine Int. 225 241 (2014).
[10] C. Y. Wu et al., Technical report LNLL/Rochester 2007 TRIUMF activity (2007).

Speaker: Giacomo Colombi (University of Guelph)

6:13 p.m. Ab initio study of 7Li with coupled mass partitions

Lithium plays an important role in nuclear astrophysics, fusion energy generation, and nuclear technology. From a theoretical point of view, the nucleus $^7$Li presents a remarkable challenge, as its bound states and resonances can be understood as being formed by a $^4$He and $^3$H pair, or simultaneously, a single neutron/proton coupled to a $^6$Li/$^6$He core. In light of this complexity, a consistent description of $^7$Li bound-state and continuum properties in a unified model presents a significant advancement towards a predictive theory of nuclear structure and reactions. Towards achieving such a predictive description, we carried out calculations for $^7$Li within the ab initio no-core shell model with continuum (NCSMC), which is capable of describing both bound and scattering states in a unified framework, taking into account the mass/charge partitions $^4$He + $^3$H, $^6$Li + n, and $^6$He + p in a single coupled-channels calculation, using chiral nuclear forces as input. These calculations are the first ever application of the NCSMC with three coupled partitions. I will show the effects of the coupling of the partitions on the spectrum of $^7$Li and present cross sections of charge-exchange and nucleon-transfer reactions, calculation of which is allowed by the coupling.

Speaker: Jakub Herko (TRIUMF)

6:14 p.m. Beta-Delayed Charged-Particle Emission from 20Mg

One of the most important nuclear reactions in astrophysics is the 15O(α,γ)19Ne(p,γ)20Na reaction, which provides a possible breakout pathway from the hot CNO cycle in stars. Studying this reaction directly in the laboratory is challenging, instead, an indirect study using β-decay proton and α decays of 20Mg was performed at TRIUMF. The experiment used the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) to detect gamma rays and, for the first time, the Regina Cube for Multiple Particles (RCMP), a newly developed silicon detector array designed to detect low-energy protons and alpha particles. This setup enables the most sensitive search to date for rare decay branches and gamma-ray transitions from astrophysically important states. This talk will describe the analysis of 20Mg decay and what it can tell us about the resonances that play a key role in stellar nucleosynthesis.

Speaker: Sydney Plante (University of Regina)

6:15 p.m. A data-driven approach to learning about nuclear structure

Historically, students entering the field of nuclear structure learn about the topic through encountering models. Often, the order in which models are presented echoes the chronology of discoveries within the topic. Students are then provided with one or two selected examples of nuclear data which strongly support a particular model. In this way, they often fail to achieve a wider understanding of the field or the utility of particular models.

We have been pioneering an alternative pedagogical approach to nuclear structure, starting with the data and seeing how that suggests models rather than reverse. Access to large databases of validated data is a particular feature of nuclear structure, unusual to other fields, and naturally associated with the societal relevance of such data. This abundance of data encourages student-led investigations. It also leads to an appreciation of which models have the widest utility in describing nuclei such as the rotational model while the extreme independent particle model is applicable to very few extant cases. We have developed a series of textbooks that follow this Nuclear Data approach, starting with Nuclear Data: A Primer. This was followed with intermediate level textbooks entitled and Nuclear Data: A Collective Motion View and Nuclear Data: An Independent-Particle Motion View.

In this presentation, we will give an overview of the philosophy beyond our pedagogical approach providing some interesting examples. We will emphasise the potential for future applications of techniques in Data Science and Machine Learning. Such interdisciplinary approaches to the data may lead to new insights especially those driven by students who approach the subject with a fresh pair of eyes.

Speaker: David Jenkins (University of York)

6:16 p.m. Decay Spectroscopy of 161Eu with the GRIFFIN Spectrometer

The neutron-rich Gadolinium isotopes around mass A=160 represent a critical region for understanding both nuclear structure and astrophysical nucleosynthesis. These nuclei exhibit large prolate deformations and lie along the freeze-out path of the rapid neutron capture process (r-process). Understanding their structure can give insight into the rare-earth abundance peak formation. The odd-mass isotope (N=97) provides a sensitive probe of the single-particle spectrum in this deformed region through its one-neutron excitation experiments relative to the well-studied even-even core. The low-lying single-neutron states have been probed via the ${}^{160}$Gd(d,p) reaction, and several Nilsson configurations were suggested. The study of the excited states via the neutron capture reaction provided very limited information on the gamma-ray decays, and the previous study by beta-decay placed only four transitions in the decay scheme. The present work reports new high-precision measurements of excited states following beta-decay of high-purity beams produced at the TRIUMF-ISAC facility. To avoid molecular and isobaric contamination, IGLIS(Ion Guide Laser Ion Source) was used along with the ISAC mass separator to greatly improve beam purity with two-step laser ionization selecting Eu isotopes only. Using the GRIFFIN high-efficiency gamma-ray spectrometer augmented with the PACES conversion electron spectrometer and beta-particle tagging with the Zero Degree Scintillator, this work has identified 87 new gamma-ray transitions and constructed a level scheme comprising 35 new excited states. The half-life has been remeasured with improved precision. An overview of the experiment and analysis will be provided with these results, providing stringent tests of the Nilsson model in the midshell region and delivering crucial nuclear structure inputs for r-process calculations.

Speaker: Jizhong Liu (TRIUMF/UVic)

6:17 p.m. Beyond Sphericity in a Semi-Magic Nucleus: Multiple Shape Coexistence in $^{116}$Sn

The evolution of nuclear shapes and the phenomenon of shape coexistence lie at the heart of our understanding of nuclear structure and the effective nuclear interaction. While dramatic examples of shape coexistence have long been established near closed shells, semi-magic nuclei have traditionally been regarded as structurally simple systems, dominated by pairing correlations and spherical mean fields. In this context, the tin isotopic chain, anchored by the robust $Z=50$ shell closure, has served for decades as the textbook paradigm of sphericity and seniority-driven structure.

This contribution will present compelling experimental evidence that fundamentally challenges this long-standing picture. Using a high-precision Coulomb-excitation experiment on $^{116}$Sn, located at the midpoint of the neutron mid-shell, an extensive and internally consistent set of electromagnetic matrix elements has been extracted. These data enable, for the first time in this nucleus, a fully model-independent determination of intrinsic quadrupole deformations for the ground and excited $0^+$ states, as well as spectroscopic quadrupole moments for multiple low-lying $2^+$ states.

The results reveal a remarkably rich and unexpected structural landscape. Rather than a spherical ground state weakly perturbed by a single intruder configuration, $^{116}$Sn exhibits multiple coexisting shapes at low excitation energy. The ground state itself is shown to possess a small but finite oblate deformation, incompatible with spherical symmetry and characterized by limited shape fluctuations. In addition, two excited $0^+$ states display distinct intrinsic deformations, providing unambiguous evidence for multiple-shape coexistence -a phenomenon observed in only a handful of nuclei across the entire nuclear chart.

These findings are discussed in the context of the experiment-driven Three-Band Mixing (3BM) model developed specifically for this work, as well as the Projected Generator Coordinate Method (PGCM) framework. Together, these approaches reveal strongly fragmented wave functions for the $0^+$ states, in stark contrast to the largely unperturbed nature of the $2^+$ states, and provide a coherent explanation of longstanding anomalies observed in nucleon-transfer reactions.

These results demonstrate that even semi-magic nuclei can host complex collective dynamics and multiple competing shapes. The case of $^{116}$Sn thus emerges not as an exception, but as a key benchmark for testing modern nuclear structure theories beyond the traditional limits of shell closures.

Speaker: Marco Siciliano (Argonne National Laboratory)

6:18 p.m. Mirror energy differences in $T_z=\mp3/2$ nuclei $^{45}$Cr and $^{45}$Sc

Isospin symmetry implies that the nuclear force acts in the same way between proton-proton, neutron-neutron and proton-neutron pairs in the atomic nucleus. To probe this symmetry, it is possible to study the so-called "mirror nuclei" that have interchanged numbers of protons and neutrons and thus should have analogous structures. Leaving aside the Coulomb interaction, the difference in excitation energy of the states characterised by the same isospin in mirror nuclei, called mirror energy differences (MED), are signatures of isospin symmetry breaking [1].
The proton-rich members of the mirror pairs are challenging to to produce and populate in high-spin states. In a recent experiment performed at the Accelerator Laboratory of the University of Jyväskylä the 3-proton excess nucleus $^{45}$Cr, a $T$=3/2 mirror of $^{45}$Sc, was studied using the MARA separator [2] and the JUROGAM3 spectrometer [3]. $^{45}$Cr was produced in the 3-neutron evaporation channel of the $^{24}$Mg+$^{24}$Mg fusion-evaporation reaction at different beam energies. Although this reaction channel is strongly suppressed in terms of production cross section with respect to the other evaporation channels, the $^{45}$Cr evaporation residues were unambiguously identified at the MARA focal plane by exploiting the characteristic $\beta$-delayed proton emission decay mode of this nucleus [4].
Previous works investigated the mirror energy differences of the $^{45}$Cr-$^{45}$Sc mirror pair produced in two-nucleon knockout up to the $J$=$11/2$ states [5] and carried out a sensitivity study of the MED in positive parity bands [6].
Our work aims at extending the level scheme of $^{45}$Cr and comparing our results with predictions from the shell model calculations. The half-life of the $3/2^+$ isomeric state in $^{45}$Cr could also be measured in our experiment. In addition to that, the experimental 3-neutron evaporation production cross section for $^{45}$Cr was extracted as a function of the excitation energy. The experimental results were compared with the predictions of PACE4 [7] and GEMINI++ [8] fusion-evaporation simulation codes, which produce discordant results that differ for a few orders of magnitude. This result can be particularly useful when planning further experiments in this mass region of the $N$=$Z$ line.

References
[1] M. Bentley and S. M. Lenzi, Progress in Particle and Nuclear Physics,
59, 497 (2007)
[2] J. Sarén et al., Nucl. Instrum. Methods B 266, 4196 (2008)
[3] J. Pakarinen, J. Ojala, P. Ruotsalainen et al., Eur. Phys. J. A 56, 149 (2020)
[4] C. Dossat et al., Nucl. Phys. A 792, 18 (2007)
[5] S. Uthayakumaar, M. A, Bentley, E. C. Simpson et al., Phys. Rev. C 106, 024327 (2022)
[6] W. Satuła, M. A. Bentley, A. Jalili and S. Uthayakumaar, Phys. Rev. C
108, 044315 (2023)
[7] A. Gavron, Phys. Rev. C 21, 230, (1980)
[8] R. J. Charity, Phys. Rev. C 82 014610 (2010)

Speaker: Denise Lazzaretto (University of Jyväskylä)

6:19 p.m. Lifetime measurements of excited states of $^{210}$Pb and $^{200}$Pt applying the two-neutron transfer reaction*

Low-spin and low-energy observables give access to the underlying nuclear structure of atomic nuclei. Moderately neutron-rich radioactive isotopes can efficiently be provided by the ($^{18}$O, $^{16}$O) two-neutron transfer reaction. The population of low-spin excited states allows measurements of their $\gamma$-ray coincidences and lifetimes, hence, electromagnetic matrix elements.
Improved microscopic understanding of cosmic nucleosynthesis calls for more precise and complete data on neutron-rich nuclei in the mass region around the doubly-magic nucleus $^{208}$Pb that serve to constrain microscopic nuclear models [1]. In particular, the $B(E2)$$\downarrow$ values of yrast transitions of $^{210}$Pb partially show discrepancies with shell-model calculations. However, the uncertainty of the adopted $B(E2; 2^+_1 \rightarrow 0^+_1)$ value [2] was too large to conclusively compare the experimental and theoretical results. Therefore, $^{210}$Pb was investigated in an experiment at the 10 MV FN-tandem accelerator at the University of Cologne.
Furthermore, the W, Os, Pt and Hg region of the nuclear chart exhibits phase transitions between oblate, prolate and spherical shapes [3, 4]. The energy ratio $R_{4/2} = E(4^+_1)/E(2^+_1)$ indicates a transition from $\gamma$-softness towards sphericity for the Pt isotopic chain when approaching the neutron-shell closure at $N = 126$. $^{200}$Pt with $N = 122$ could mark the transitional point between the $\gamma$-soft nuclei $^{196, 198}$Pt and the semi-magical, supposedly spherical $^{204}$Pt and was studied at the 9 MV tandem accelerator at the IFIN-HH in Bucharest-Măgurele. Besides the $R_{4/2}$ ratio, the $B_{4/2}$ ratio of the $B(E2)$$\downarrow$ values of the $4^+_1 \rightarrow 2^+_1$ and $2^+_1 \rightarrow 0^+_1$ transitions serves as a complementary indicator for nuclear structure.
The $B(E2)$$\downarrow$ value is inversely proportional to the lifetime of the de-exciting state. Therefore, we performed lifetime measurements applying the recoil-distance Doppler-shift method [5]. Our significantly more precise result for the $B(E2; 2^+_1 \rightarrow 0^+_1)$ value of $^{210}$Pb enhances the comparability to shell-model calculations, underlining a discrepancy in a consistent shell-model description of the $B(E2; 2^+_1 \rightarrow 0^+_1)$ and $B(E2; 4^+_1 \rightarrow 2^+_1)$ values [6]. Further, we measured the lifetimes of the $2^+_1$ and $4^+_1$ states of $^{200}$Pt allowing for the calculation of the $B_{4/2}$ ratio, which shows good agreement with the theoretical limit of a spherical nucleus, indicating the structural evolution within the Pt isotopic chain [7, 8].

[1] D. Kocheva et al., Eur. Phys. J. A 53, 175 (2017).
[2] C. Ellegaard et al., Nucl. Phys. A 162, 1 (1971).
[3] J. Jolie et al., Phys. Rev. C 68, 031301 (2003).
[4] E. Sahin et al., Phys. Lett. B 857, 138976 (2024).
[5] A. Dewald et al., Prog. Part. Nucl. Phys. 67, 786 (2012).
[6] C. M. Nickel et al., Phys. Rev. C 113, 014329 (2026).
[7] C. M. Nickel et al., Phys. Rev. C (2026, accepted).
[8] A. Esmaylzadeh et al., Nucl. Phys. A (2026, accepted).

*Supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) as part of the Project-ID No. 264883531 - Research Training Group 2128 'Accelence' and Project-ID No. 499256822 - Research Training Group 2891 'Nuclear Photonics' and by the German Federal Ministry of Education and Research (BMBF) under Grant No. 05P21RDCI2.

Speaker: Mr C.M. Nickel (Institute for Nuclear Physics, Dept. of Physics, Technische Universität Darmstadt, Darmstadt, Germany)

6:20 p.m. Emergence of quadrupole collectivity near shell closures

Quadrupole collectivity near shell closures dominates the structure of low-lying excited states. The $B_{4/2}=\frac{B(E2;\, 4_1^+\to2_1^+)}{B(E2;\, 2_1^+\to0_1^+)}$ ratio as a measure of collectivity takes benchmark values in the collective limits of a spherical harmonic vibrator with $B_{4/2}^{\text{vib}}= 2$, or quadrupole-deformed limits with $B_{4/2}^{\text{rot}} = 1.43$, regardless of axial symmetry. For near-magic nuclei with seniority-dominated low-lying states, $B_{4/2}$ can take values even lower than unity. For $^{132}_{\phantom{1}52}$Te with its proximity to the $Z = 50$ and $N = 82$ shell closures this quantity will serve as an indicator of the balance between spherical-collective and spherical-seniority dominated structures.

The isoscalar proton-neutron symmetric $2_1^+$ state and the isovector mixed-symmetry $2^+_{\text{1,ms}}$ state are predominantly of one-quadrupole phonon character. Therefore, the properties of these states also give insights into the nuclear structure. The isotope $^{132}$Te is of particular interest since it is close to and an isobar of the doubly magic $^{132}$Sn. With only two valence protons and two valence-neutron holes, the mixing of the respective proton and neutron configurations into the wave functions is of utmost importance, as it constitutes the foundation for more complex collective states when turning to larger valence spaces.

Our recent lifetime measurements at IFIN-HH Bucharest [1] and IKP Cologne [2] on $^{132}$Te show emerging collectivity and complement the investigation of mixed-symmetry states in the $N=80$ isotonic chain. Here the $^{130}$Te($^{18}$O,$^{16}$O)$^{132}$Te two-neutron transfer reaction was employed to produce the radioactive $^{132}$Te. Shell model calculations have been performed to compare the contributions of different configurations to the wave function.

In a further study, $^{212}_{\phantom{2}88}$Ra is studied which is with $N=124$ in proximity to the neutron-shell closure at $N=126$. A radioactive $^{212}$Ra ion beam was provided by HIE-ISOLDE to explore the collectivity of its first excited $2^+$ state.

[1] T. Stetz, H. Mayr et al., Phys. Rev. C 112, 034325 (2025)

[2] H. Mayr, T. Stetz et al., Phys. Rev. C 113, 014318 (2026)

Supported by the BMFTR under grant numbers 05P21RDFN9, 05P21RDCI2 and 05P24RD3.

Speaker: Hannes Mayr

6:21 p.m. Probing the s-process via Exclusive Indirect Measurement of the $^{22}Ne(\alpha, \gamma)^{26}Mg$ Reaction

The slow neutron capture process (s-process) creates almost half of the elements heavier than iron in the universe. One of the most important neutron sources for the s-process is the $^{22}Ne(\alpha, n) ^{25}Mg$ reaction, which competes with the $^{22}Ne(\alpha, \gamma) ^{26}Mg$ reaction. The current nuclear data for these reactions show great discrepancies. Thus, in order to understand the synthesis of heavy elements, it is crucial to study the ratio between these two reactions.

Using the EMMA mass spectrometer and TIGRESS $\gamma$-ray spectrometer at TRIUMF, our goal is to indirectly measure the $^{22}Ne(\alpha, \gamma) ^{26}Mg$ reaction. The experiment involves bombarding a $LiF$ target with $^{22}Ne$ beam. A silicon detector is used to detect light ejectiles, the TIGRESS array is used to detect the $\gamma$-rays from the reactions, and the EMMA spectrometer to select the recoils of interest. Different coincidence measurements between the three detectors allows us to measure the particle spectroscopic factors for states above the neutron threshold.

In this talk, I will present the preliminary results and work in progress, as well as the major challenges we face.

Speaker: Mike Qiu (TRIUMF)

6:22 p.m. Measuring 39K(3He,α)38K with GODDESS to search for energy levels in 38K important for the 37Ar(p,γ)38K reaction rate

The 37Ar(p,γ)38K reaction plays a critical role in determining the abundances of several stable isotopes at the endpoint of rp-process nucleosynthesis in novae. To inform the astrophysical reaction rate of proton capture on 37Ar and guide any future direct measurements, a better understanding of the 38K energy levels above the 37Ar+p threshold is essential. Experimentally, these excited states of 38K just above the proton threshold may be probed through alternative, experimentally-accessible reactions.

To this end, the 39K(3He,αγ)38K reaction in regular kinematics was measured. The ATLAS accelerator at Argonne National Laboratory provided a beam of 3He at 30 MeV/u, which was incident on an enriched potassium-39 target. Gamma rays and charged particles were detected using the GODDESS system, comprised of the Oak Ridge Rutgers University Barrel Array (ORRUBA) for charged particles, and the Gamma Ray Energy Tracking In-beam Nuclear Array (GRETINA) for gamma rays. The spectroscopy provides information on the excited states of 38K, including those near the proton separation energy of 5.2 MeV. Experimental constraints on the energies and spin-parities of low-spin states in this region, which are of astrophysical importance, as well as their implications for the rp-process, will be discussed.

Speaker: Ashwin Nagarajan

6:23 p.m. Excitation energies of the low-lying isomeric states in 100-Y and 102-Y

Beta-decaying, spin-trap isomers have been observed in $^{96}$Y, $^{98}$Y and $^{100}$Y with half-lives ranging from 9 to 0.7 seconds [Ab08,Ch20,Si21]. A recent paper [Ca25] has investigated the isomeric-yield ratio in production of all three in fission and observed that, in $^{96}$Y and $^{100}$Y it is the higher-spin state which is populated more strongly, whereas in $^{98}$Y the opposite situation is observed. Moreover, Cannarozzo et al., [Ca25] concluded that in $^{100}$Y the higher-spin state is the ground state which is opposite to the ordering in [Si21]. In $^{102}$Y there are two beta-decaying states which have similar half lives (t$_{1/2}$ = 360(40) ms [Sh83] and 300(10) ms [Hi91]) and a small energy difference, making it difficult to measure their relative energy. Data measured at the JOSEF recoil separator at Jülich [Sh83] indicates that it is the high-spin state that is preferentially populated in the thermal fission of $^{235}$U but it is still unknown whether this is the ground- or isomeric state.
This presentation will report on the use of the Phase Imaging – Ion cyclotron Resonance (PI-ICR) method [El13] at the JYFLTRAP double Penning trap at the IGISOL facility at the University of Jyväskylä, Finland to measure the relative energies of the beta-decaying states in $^{102}$Y and re-measure $^{100}$Y. The nuclei of interest were produced via induced fission of $^{238}$U using a 30 MeV proton beam. In $^{100}$Y a value of 147.8(42) keV was measured for the excitation energy of the isomeric state, which overlaps with the previously measured value of 145(15) keV [Ha07] and reduces the experimental error by a factor of 4. In $^{102}$Y the closeness in energy of the 2 states makes the analysis quite complicated and although the two states were not fully separated, the observed mass distribution can be fitted with a bi-modal distribution with preliminary analysis indicating an excitation energy of ~10 keV for the isomeric state. Details of the experiment and of the analysis procedures will be discussed.

References
[Ab08] D.Abriola and A.A.Sonzogni, Nuclear Data Sheets 109 (2008) 2501.
[Ca25] S.Cannarozzo et al., Physics Letters B871 (2025) 1.
[Ch20] J.Chen and B.Singh, Nuclear Data Sheets 164 (2020) 1.
[El13] S.Eliseev et al., Applied Physics B: Lasers and Optics 114 (2013) 396.
[Ha07] U.Hager et al., Nuclear Physics A793 (2007) 20.
[Hi91] John C. Hill et al., Physical Review C43 (1991) 2591.
[Sh83] K.Shizuma et al., Physical Review C27 (1983) 2869.
[Si21] B.Singh and J.Chen, Nuclear Data Sheets 172 (2021) 1.

Speaker: A.M. Bruce (University of Brighton)

6:24 p.m. Nuclear structure of 94Pd at transition-point between the isoscalar and isovector characteristics

Nuclei near the doubly magic nucleus $^{100}$Sn ($N=Z=50$) have been extensively studied to investigate nuclear structure, including shell evolution, seniority effects, and proton–neutron interactions. In this work, $^{94}$Pd with $N=Z+2$ was investigated with a focus on isovector($T=1$) and isoscalar($T=0$) neutron-proton pairing using the fast-timing measurement. Half-lives of yrast excited states in $^{94}$Pd were measured using isomeric decay spectroscopy. The experiment was performed at RIBF (Radioactive Isotope Beam Factory), RIKEN, where $^{94}$Pd ions were produced via in-flight fragmentation of a $^{124}$Xe beam impinging on a $^{9}$Be target. These ions were implanted into the GARi active stopper array, and isomeric delayed $\gamma$ rays were detected with the IDATEN fast-timing array consisting of 48 LaBr$_{3}$(Ce) detectors. The half-lives were determined using the generalized centroid difference method, yielding the $T_{1/2}$ values of $\leq 15$ ps, $13(11)$ ps, $\leq 13$ ps, $693(72)$ ps, and $\leq 19$ ps for the $(2^{+}_{1})$, $(4^{+}_{1})$, $(6^{+}_{1})$, $(8^{+}_{1})$, and $(10^{+}_{1})$ states, respectively. The half-lives of the $(2^{+}_{1})$, $(4^{+}_{1})$ and $(10^{+}_{1})$ states are reported here for the first time, and the uncertainties of the half-lives of the $(6^{+}_{1})$ and $(8^{+}_{1})$ states have been improved compared to previous measurements. Reduced transition probabilities $B(E2)$ were deduced from the measured half-lives and discussed in the context of shell-model calculations employing the JUN45 effective interaction, including $T=0$, $T=1$ and full interaction. The results suggest that $^{94}$Pd, with $N=Z+2$, lies in a transitional regime between the $N=Z$ isoscalar-pairing domain ($^{92}$Pd) and the $N=50$ isovector-dominated region ($^{96}$Pd).

Speaker: Youngseub Jang (Korea University, Center for Exotic Nuclear Studies, Institute for Basic Science)

6:25 p.m. Enabling Systematic Nuclear Structure Studies Through Automated Level-Scheme Construction

Recent decades have witnessed exponential growth in both the quality and volume of experimental nuclear data, driven by advancements in detector technologies and accelerator capabilities. Gamma-ray spectroscopy has particularly benefited from these improvements, with large-scale spectrometers such as GRIFFIN and TIGRESS at TRIUMF enabling collection of increasingly complex, high-dimensional datasets containing hundreds of transitions. Level schemes—the excited-state energies and decay pathways of nuclei—are fundamental to nuclear structure research, yet their construction from spectroscopic data remains a months-to-years manual process of visual pattern recognition, coincidence gating, and iterative refinement. This research reformulates level-scheme construction as a constrained inverse problem, taking γ-ray singles spectra and symmetric coincidence matrices as inputs and recovering directed decay networks.
The approach addresses key challenges inherent to real data: the undirected nature of coincidence measurements, irresolvable doublets, missing weak transitions, and detector artifacts. Building on transition-matrix formalism that analytically relates scheme connectivity to measured intensities, we develop a three-stage pipeline: a probabilistic data layer encoding measurement uncertainties, a learned proposal layer that captures structural priors to constrain combinatorial search, and a physics-enforcing inference layer ensuring energy consistency and intensity-flow conservation.

Speaker: Samantha Buck (University of Guelph)

6:26 p.m. Level Structure and Electromagnetic Transition Character in 158Er from Beta Decay of 158Tm

In nuclei near N∼90, low-lying level schemes often contain several unplaced transitions, and many excited states lack definitive spin and multipolarity assignments. This limits the extraction of electromagnetic matrix elements and hinders detailed interpretation of configuration mixing and nuclear structure. The structure of 158Er has been investigated following the β decay of 158Tm using the GRIFFIN spectrometer.
Internal conversion coefficients (ICCs) were determined from measured electron and γ-ray intensities and compared with theoretical values to establish transition multipolarities. Seventeen transitions have been assigned definitive multipolarities, and the spin-parity of twelve excited states were constrained or newly assigned. Six transitions exhibit enhanced ICC values relative to theoretical expectations, indicating multipole mixing with contributions consistent with E0 admixtures; these preliminary results will be presented.

Speaker: Abraham Avaa (TRIUMF)

6:27 p.m. Neutron capture resonance structure and cross section measurements of 243Am

The long-term management of high-level nuclear waste will necessarily involve the transmutation of highly radioactive materials using accelerator-driven systems converting long lived radioactive waste products into short-lived or stable nuclei. Am is the most abundant, long lived radioactive product in high-level nuclear waste, but the neutron capture cross section is known with high-level uncertainty (>10 %), whereas uncertainties of approximately 2% are needed for transmutation.

Such studies presents challenges, including the difficulties of working with actinide materials and the complexity of analyzing the abundant resonance structures. We have made significant progress in producing and handling of actinide targets generally, and Am specifically. We implement solution combustion synthesis methods to make robust targets on a variety of backing materials. An initial measurement at the LANSCE facility, using the DANCE 4π array of 160 BF2 detectors and the neutron time-of-flight technique, showed that the purity of the target can yield precise cross sections, resolving the fine resonance structures in 243Am(n,γ). We intend to present our preliminary results.

This work is funded by the National Nuclear Security Administration under Grant # NA0004256.

Speaker: Wanpeng Tan

6:28 p.m. Structure of Neutron-Rich $^{33,34,35}$Mg from $\beta$ Decay Studies

The structure of neutron-rich magnesium isotopes in the vicinity of the so-called Island of Inversion provides a sensitive testing ground for nuclear models and shell evolution far from stability. In this work, we investigate the $\beta$ decay of $^{33,34,35}\mathrm{Mg}$ using high-efficiency $\gamma$-ray spectroscopy in combination with $\beta$ tagging. The experiment was performed using the GRIFFIN spectrometer at TRIUMF, with radioactive beams delivered by the ISAC facility. For $^{33}\mathrm{Mg}$, the primary objective is to constrain the spin and parity of its ground state through a detailed study of $\beta$ feeding to states in $^{33}\mathrm{Al}$. In particular, the extraction of ground-state feeding and the associated $\log ft$ values provides key information on the allowed or forbidden nature of the transitions, offering insight into the underlying nuclear configurations. The $\beta$ decay of $^{34}\mathrm{Mg}$ populates excited states in $^{34}\mathrm{Al}$, a nucleus known for its complex structure and the coexistence of different configurations. We extend previous studies by refining the level scheme and performing $\gamma$--$\gamma$ angular correlation measurements to assign spin and parity to low-lying states. For $^{35}\mathrm{Mg}$, a comprehensive analysis of $\beta$-delayed $\gamma$ rays has been performed. A new level scheme for $^{35}\mathrm{Al}$ is established based on coincidence relationships and cycle-based decay fitting. From this analysis, $\beta$-feeding intensities and corresponding $\log ft$ values are extracted, providing constraints on transition strengths and nuclear structure. Overall, these results contribute to a more coherent picture of shell evolution and configuration mixing in neutron-rich nuclei around $N \approx 20$. These results are compared with shell-model calculations and state-of-the-art ab initio approaches to assess the predictive power of nuclear structure models in this region.

S. Sekal$^1$,
M. M. Rajabali$^1$,
D. Moye$^1$,
E. Vespie$^1$,
Y. Hassan$^1$,
R. S. Lubna$^2$,
G. C. Ball$^2$,
A. B. Garnsworthy$^2$,
A. Volya$^3$,
C. R. Natzke$^{2,4}$,
A. T. Laffoley$^5$,
C. Andreoiu$^8$,
D. Annen$^8$,
M. Berube$^2$,
S. S. Bhattacharjee$^2$,
H. Bidaman$^5$,
V. Bildstein$^5$,
R. Caballero-Folch$^2$,
G. Carpenter$^{2,6}$,
R. Coleman$^5$,
I. Dillmann$^{2,7}$,
F. H. Garcia$^8$,
S. Gillespie$^{2,9}$,
E. Gopaul$^2$,
B. Greaves$^5$,
C. J. Griffin$^2$,
G. Hackman$^2$,
S. Hodge$^2$,
R. Kanungo$^{11}$,
V. Karayonchev$^2$,
A. Kindred$^1$,
G. Leckenby$^2$,
L. Mantle$^2$,
K. Mastakov$^5$,
J. McAfee$^{2,10}$,
S. Nittala$^2$,
B. Olaizola$^{2,12}$,
G. Pasquino$^2$,
C. Paxman$^{2,10}$,
C. Petrache$^{17}$,
C. Porzio$^{2,13}$,
R. Preshong$^1$,
E. Raleigh-Smith$^2$,
M. Rocchini$^5$,
W. Royer$^{2,10}$,
R. Russell$^{10}$,
Y. Saito$^{2,14}$,
P. Spagnoletti$^8$,
C. E. Svensson$^5$,
R. Umashankar$^{2,14}$,
S. Valbuena$^5$,
V. Vedia$^2$,
E. White$^1$,
K. Whitmore$^8$,
J. Williams$^2$,
F. Wu$^8$,
T. Zidar$^5$,
J. D. Holt$^2$,
T. Miyagi$^{15}$

$^1$ Department of Physics, Tennessee Technological University, Cookeville, Tennessee 38505, USA

$^2$ TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada

$^3$ Department of Physics, Florida State University, Tallahassee, Florida 32306, USA

$^4$ Department of Physics, Colorado School of Mines, Golden, CO 80401, USA

$^5$ Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada

$^6$ School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom

$^7$ Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2, Canada

$^8$ Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada

$^9$ Present address: National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA

$^{10}$ Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom

$^{11}$ Department of Astronomy and Physics, Saint Mary's University, Halifax, NS B3H 3C3, Canada

$^{12}$ Present address: ISOLDE-EP, CERN, CH-1211 Geneva 23, Switzerland

$^{13}$ INFN Sezione di Milano and Dipartimento di Fisica, Università di Milano, Milano, Italy

$^{14}$ Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4, Canada

$^{15}$ Theory Center, Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany

$^{17}$ IJCLab, Université Paris-Saclay, CNRS/IN2P3, 91405 Orsay, France

Speaker: Dr Smain Sekal (Tennesse tech university)

6:29 p.m. Insight on shape coexistence in $^{100}$Zr through lifetime measurements at GRIFFIN

The sudden onset of deformation in $A\approx100$ nuclei at $N=60$ has been described as a ground-state shape transition that has raised a lot of interest over the years from an experimental and theoretical point of view [1]. This transition is most pronounced in the Zr and Sr isotopic chains where the low-energy excited-state structure shows significant signs of deformation developing at $N=60$, as opposed to the spherical-like structure observed at $N\leq58$.

At present, the two most promising theoretical interpretations of this phenomenon are given by the Monte Carlo Shell Model (MCSM) [2] and the Interacting Boson Model with Configuration Mixing (IBM-CM) [3]. The MCSM calculations interpret the structure of $^{100}$Zr within a multiple-shape-coexistence scenario with several distinct deformed shapes predicted for the lowest $0^+$ states, with rotational bands built on top of them. In contrast, the IBM-CM calculations predict a weakly-deformed "intruder" ground-state configuration in $^{100}$Zr, with corresponding $\beta$ and $\gamma$ bands, and a low-lying spherical "normal" configuration.

In order to test these theoretical models an experiment was performed at the TRIUMF-ISAC facility to investigate the structure of $^{100}$Zr following the $\beta$ decay of $^{100}$Y by utilizing the GRIFFIN $\gamma$-ray spectrometer [4]. The 15 HPGe clover detectors of GRIFFIN were coupled with seven LaBr$_3$ detectors for fast-timing lifetime measurements, and the PACES array for conversion electrons.

Mainly low-spin excited states were populated in the $\beta$ decay of the $1^-$ state in $^{100}$Y. This allowed for the lifetimes of several key non-yrast excited states in $^{100}$Zr, including those of the $2^+_2$ and $0^+_3$ states, to be extracted for the first time in this study using the Generalized Centroid Difference method. These new results will be presented and compared to the MCSM and IBM-CM theoretical predictions. Evidence supporting the shape-coexistence scenario in $^{100}$Zr will be presented, together with the notable structural similarities between $^{100}$Zr and $^{98}$Sr.

[1] P.E. Garrett et al., Prog. Part. Nucl. Phys. 124 (2022) 103931.
[2] T. Togashi et al., Phys. Rev. Lett. 117 (2016) 172502.
[3] N. Gavrielov et al., Phys. Rev. C 99, 064324 (2019).
[4] A.B. Garnsworthy et al., NIM A, 918 (2019).

Speaker: Konstantin Stoychev (University of Guelph)

6:30 p.m. Study of Multiple Shape Coexistence in 110Cd

Cd isotopes, particularly $^{110,112}$Cd, have long been considered the best examples of nuclei with vibrational behaviour. However, recent studies challenge this interpretation, suggesting that Cd isotopes possess characteristics of multiple shape coexistence. To further investigate this issue, a series of $\beta$-decay experiments were conducted to improve the spectroscopic information on $^{110,112}$Cd. The obtained results will be crucial for the complementary Coulomb-excitation studies that aim to determine the intrinsic shapes of low-lying 0$^{+}$ states.

The current work examines the nuclear structure of $^{110}$Cd through the $\beta-$ decay of $^{110}$Ag and the $\beta+$/EC decay of $^{110}$In conducted at the TRIUMF-ISAC facility. The radioactive-ion beams of $^{110}$Ag and $^{110}$In were delivered to a mylar tape located at the centre of the GRIFFIN spectrometer, which consisted of 15 HPGe clover detectors with BGO Compton-suppression shields.

The obtained $\gamma$-$\gamma$ coincidence data was used to construct a level scheme of $^{110}$Cd, to confirm previously observed in-band transitions, and to seek evidence for rotational bands in $^{110}$Cd. In this presentation, selected preliminary results and key findings will be discussed.

Speaker: Samantha Lange (University of Guelph)

6:31 p.m. Coulomb excitation of 110Cd studied with AGATA at LNL

For several decades, stable even-mass Cd isotopes have been considered to be textbook examples of multiphonon spherical vibrators [1] based on the excitation energy pattern of their low-lying states. However, a detailed study of $^{110}$In $\beta$ decay and subsequent beyond-mean-field theoretical calculations [2-6] suggested instead the presence of multiple shape coexistence in the $^{110}\text{Cd}$ and $^{112}\text{Cd}$ isotopes. To verify this hypothesis, it is essential to determine the shapes of low-lying $0^+$ states in stable even-even Cd nuclei. The Coulomb-excitation method [7], which enables a model-independent analysis of nuclear shapes through the use of quadrupole sum rules [7], provides a powerful tool for this type of research.

The Coulomb excitation of $^{110}\text{Cd}$ using a 187-MeV $^{60}$Ni beam was performed at the National Institute for Nuclear Physics - Legnaro National Laboratories, Italy [8]. This experiment was a part of a broader program focused on systematic Coulomb-excitation studies of $^{110}\text{Cd}$ initiated with measurements using $^{14}$N and $^{32}$S beams at the Heavy Ion Laboratory, University of Warsaw [6]. The program also included a measurements with a heavier reaction partner $^{208}$Pb, which was performed at Argonne National Laboratory, USA [9].

The $^{60}$Ni + $^{110}\text{Cd}$ experiment was carried out using the AGATA $\gamma$-ray tracking spectrometer [10,11] and the particle detection array SPIDER [12]. In total 20 states of both negative and positive parities were populated up to 3.2 MeV of excitation energy, including, in particular, the $0^+_3$ state at 1731 keV. The on-going analysis focuses on the extraction of the $\gamma$-ray intensities from which a set of electromagnetic matrix elements in $^{110}\text{Cd}$ will be obtained, including quadrupole moments of excited states. This will provide insight into the nuclear shape of the $0^+_2$ and $0^+_3$ states. The quadrupole deformation parameters for the $0^+_{1,2}$ states obtained from the experiments with the $^{14}$N and $^{32}$S beams will be presented, along with preliminary results of the analysis of the AGATA data.

References
[1] R.F. Casten, Nuclear Structure from a Simple Perspective (Oxford Univ. Press 1990)
[2] P.E. Garrett et al., Phys. Rev. C 86 (2012) 044304.
[3] P.E. Garrett et al., Phys. Rev. C 101 (2020) 044302.
[4] P.E. Garrett et al., Phys. Rev. Lett. 123 (2019) 142502.
[5] P.E. Garrett et al., Acta Phys. Pol. B Proc. Suppl. 19 (2026) 1-A14
[6] K. Wrzosek-Lipska et al., Phys. Lett. B 875 (2026) 140315
[7] M. Zielinska, Low-Energy Coulomb Excitation and Nuclear Deformation, in: The Euroschool on Exotic Beams, vol.VI, S.M. Lenzi and D. Cortina-Gil (eds.) Lecture Notes in Physics 1005, pp. 43-86 (Springer, 2022)
[8] I.Z. Pietka et al., Acta Phys. Pol. B Proc. Suppl. 18 (2025) 2-A26
[9] S. Pannu et al., presented at Fall Meeting of the American Physical Society, Division of Nuclear Physics, 17-20 October, 2025
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[11] J.J. Valiente-Dobón et al., Nucl. Instrum. Methods A1049 (2023) 168040.
[12] M. Rocchini et al., Nucl. Instrum. Methods A971 (2020) 164030.

Speaker: Iwona Piętka (Heavy Ion Laboratory, University of Warsaw, Poland)

6:32 p.m. Towards determination of distribution of magnetization in 48K using b- NMR technique and nuclear DFT approach

Following the N=28 shell closure, a noticeable change in the slope of the charge radii, often called a "kink", has been observed in neutron-rich calcium isotopes [1,2]. However, the exact size of this kink and its underlying causes remain unclear. Theoretical predictions suggest that several factors might contribute to this behavior, including the presence of large nuclear deformations or significant radial extensions of the nuclear density distribution. To address these questions and explore the origins of the observed kink, we will determine the distribution of magnetization, specifically the differential hyperfine anomaly (also known as Bohr-Weisskopf effect), for 48K. This will be compared with the corresponding distributions in the neighboring isotopes 47K and 49K. To achieve this, we employed the b-Nuclear Magnetic Resonance (NMR) technique [3] to measure the precise magnetic moments of these isotopes. Additionally, laser-rf double resonance spectroscopy [4] will be used to determine the hyperfine structure constant (A) with high accuracy.
The data interpretation will be done with the help of nuclear density functional theory approach with angular momentum symmetry restoration [5] to analyze the variation in these moments across different angular momentum projections and mass. We employ the Hartree-Fock- Bogoliubov formalism to determine the magnetic dipole moments of the isotopes using HFODD code [6]. The spectroscopic moments are then compared with the experimental measurements. The recent results from the experiment will be presented. These findings serve as a benchmark for neutron-rich odd-odd isotopes.
References:
[1] A. Koszorus, X. Yang, W. Jiang, S. Novario, S. Bai, J. Billowes, C. Binnersley, M. Bissell, T.
E. Cocolios, B. Cooper, et al., Nature Physics 17, 439(2021).
[2] R. Garcia Ruiz, M. Bissell, K. Blaum, A. Ekstrom, N. Frommgen, G. Hagen, M. Hammen, K. Hebeler, J. Holt, G. Jansen, et al., Nature Physics 12, 594(2016).
[3] R. D. Harding et al., Phys. Rev. X 10 (2020) 041061.
[4] M.E. Van Hove and R.E. Silverans, Hyperfine Interactions, 38 (1987) 773-792.
[5] P.L. Sassarini et al., J. Phys G 49 (2022) 11LT01.
[6] J Dobaczewski et al., Phys. Rev. C 113 (2026), 024306.

Speaker: Anu Nagpal (University of York, UK)

6:33 p.m. Critical need for DSAM lifetime re-evaluations

The structure of $fp$ shell nuclei has been the subject of intensive study for many decades. These nuclei remain of crucial importance because they provide a foundation for studies of neutron-rich nuclei currently being investigated at facilities such as FRIB (e.g. [1]). Within the $fp$ shell, large-basis shell model calculations, wherein both protons and neutrons occupy the $0f_{7/2}$, $1p_{3/2}$, $0f_{5/2}$, and $0p_{1/2}$ orbits, are now routine, and can be tested against a considerable body of data [2]. Electromagnetic transition strengths provide a primary set of observables to test shell model wavefunctions, which are usually based on effective interactions derived from fits to energy levels [2].

Through the late 1960s to the early 1980s the lifetimes of many excited states in the $fp$ shell were measured by the Doppler-shift attenuation method (DSAM) with the required stopping powers evaluated using the theory of Lindhard, Scharff and Schiott (LSS) [3]. It was recently discovered [4] that the anomalously strong literature value [5] for the experimental strength of the $4^+_1 \rightarrow 2^+_1$ transition in $^{58}$Fe could be attributed to the use of LSS electronic stopping powers in Doppler-shift measurements, which for the case of $^{58}$Fe stopping in tantalum, differ by a factor of two from more recent values given by SRIM [6]. Woodside et al. [4] re-evaluated the 1978 DSAM lifetime measurement on $^{58}$Fe [7] with the LSS stopping powers replaced by values from SRIM, which brought the transition strength of the $4^+_1 \rightarrow 2^+_1$ transition into agreement with shell model calculations [2].

This example is unlikely to be unique: we have therefore begun to re-evaluate historical DSAM measurements that used LSS stopping powers. One outcome is a re-evaluation of effective charges applicable for the $fp$ shell. For example, Honma et al. [2] adopted the standard $e_p=1.5$ and $e_n=0.5$ in their comprehensive test of the GXFP1 interaction, whereas re-evaluated lifetimes in $^{54}$Cr strongly favor the "universal" effective charges $e_p=1.33$ and $e_n=0.45$ recently proposed for the $sd$ and $fp$ shells by Ogunbeku et al. [1].

An overview of the progress and implications of this work will be given, including an evaluation of the impact of historical DSAM lifetime data on extracted electric monopole ($E0$) transition strengths such as those in the Ni isotopes [8].

References
[1] T.H. Ogunbeku et al., Phys. Rev. Lett. 135 (2025) 072501.
[2] M. Honma et al., Phys. Rev. C 69 (2003) 034335.
[3] J. Lindhard, M. Scharff and H.E. Schi{\o}tt, Mat. Fys. Medd. Dan. Vid. Selsk. 33 no.14 (1963).
[4] J.A. Woodside et al., Phys. Rev. C, in press.
[5] C.D. Nesaraja, S.D. Geraedts and B. Singh, Nucl. Data Sheets 111 (2010) 897.
[6] J.F. Ziegler, M.D. Ziegler and J. P. Biersack, Nucl. Inst. Meth. Phys. Res. B 268 (2010) 1818.
[7] H.H. Bolotin et al., Nucl. Phys. A 311 (1978) 75.
[8] L.J. Evits et al., Physics Letters B 779 (2018) 396.

Speaker: Gregory Lane (The Australian National University)

6:34 p.m. Experimental Study of Low-Spin States in $^{42}$Ca and $^{44}$Ca as a Probe for Shape Coexistence

Nuclear shape coexistence plays a crucial role in understanding the microscopic origin of nuclear deformation [1-4].
In this respect, the Ca isotopic chain between the shell closures at N=20 and N=28 is an optimal test
area where different theoretical approaches can be used and their predictions compared with experimental data (\textit{e.g.} large-scale Shell Model calculations, Density Functional Theory and \textit{ab-initio} methods [5-7]).\
In this work, we report on high-precision low-spin gamma-ray spectroscopy of even-even $^{42}$Ca and $^{44}$Ca nuclei populated via thermal neutron capture reactions at the Institut Laue-Langevin (ILL).
In both $^{42}$Ca and $^{44}$Ca, the presence of $0^+$ excitations associated with deformed and superdeformed structures has already been demonstrated [8,9], however, further investigation is still essential to study other possible excitations associated with deformed configurations.
This is a complementary study to the existing analysis on the odd systems $^{41,47,49}$Ca [10], already published by this collaboration, and it aims to track the evolution of the nuclear structure along the Calcium isotopic chain.\
$^{42}$Ca and $^{44}$Ca were populated via (n$_{th}$, $\gamma$) reaction on CaCo$_3$ targets, including one enriched with radioactive $^{41}$Ca.
The $\gamma$ cascades depopulating the neutron-capture states, located at 11.5 MeV and 11.1 MeV, respectively, were detected by the HPGe FIPPS array [11].
Employing $\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$ coincidence techniques, the level schemes of $^{42}$Ca and $^{44}$Ca were significantly expanded by adding 10 and 56 new levels and 109 and 610 new transitions, respectively.
These results will be presented together with preliminary studies on $\gamma$-$\gamma$ angular correlations to establish the spin and parities of excited states.
Comparison with Shell Model calculations will also be discussed.

Bibliography
[1] K. Heyde and J. L. Wood. In: Rev. Mod. Phys. 83 (2011)
[2] P. E. Garrett, M. Zieli´nska, and E. Cl´ement. In: Progress in Particle and Nuclear Physics 124 (2022)
[3] S. Leoni et al. In: Progress in Particle and Nuclear Physics 139 (2024)
[4] S. Leoni et al. In: The European Physical Journal Special Topics 233
(2024)
[5] J. D. Holt et al. In: Phys. Rev. C 90 (2014)
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[9] C.W. Towsley, D. Cline, and R.N. Horoshko. In: Nuclear Physics A 204 (1973)
[10] S. Bottoni et al. In: Phys. Rev. C 103 (2021)
[11] C. Michelagnoli et al. In: EPJ Web Conf. 193 (2018)

Speaker: Massimiliano Luciani (Università degli Studi di Milano, INFN Sezione di Milano)

6:35 p.m. Probing Spin-Triplet Pairing Through Nuclear Mass Measurements

Nuclear masses are fundamental observables that give insight into nuclear structure, fundamental interactions, and astrophysics. Pairing gaps are an experimental observable that can be extracted from nuclear mass data and can show exotic nuclear behavior, especially for odd-even staggering and pairing effects. These pairing gaps can also provide information about nuclear deformation and the existence of the exotic state of matter known as spin-triplet pairing, especially near the $N=Z$ and $A\approx130$ region.

Multiple-Reflection Time of Flight Mass Spectrometry (MR-TOF-MS) provides high mass separation power in a short amount of time by bouncing ions between electrostatic mirrors. This increases the flight path of trapped ions, allowing ions of different mass but injected with the same energy to separate. The high mass resolving powers and short storage times have contributed to MR-TOF devices becoming common for beam purification and mass spectrometry in Rare-Isotope-Beam and accelerator facilities around the world. To search for the nucleon spin triplet pairing, we used the TRIUMF Ion Trap for Atomic and Nuclear science (TITAN) MR-TOF-MS to measure several samarium, europium, cerium, and lanthanum isotopes in the specified region.

Speaker: Alec Cannon (University of Victoria)

6:36 p.m. Measurement of the 18O(α, γ)22Ne reaction to constrain the structure properties of 22Ne resonances

Half of the elements heavier than iron in the universe are synthesized by the slow
neutron capture process ($s$-process), which occurs in asymptotic giant branch (AGB)
stars and in massive stars. The $^{18}$O(α, γ)$^{22}$Ne reaction is a key link in determining
the availability of $^{22}$Ne in the stellar environment, which affects the amount of neutrons
available for the s-process through the $^{22}$Ne(α, n)$^{25}$Mg reaction. The nuclear parameters
of some of the excited states in $^{22}$Ne play a key role in determining the thermonuclear
reaction rate. The $^{18}$O(α, γ)$^{22}$Ne reaction was measured in inverse kinematics for
the first-time using the DRAGON recoil separator at TRIUMF, Canada’s particle
accelerator centre. We studied resonance states in $^{22}$Ne with excitation energies of
10.28 and 10.29 MeV to measure their structure information, namely strengths and
energies, which will be compared with the available nuclear data. In this talk, I will
present the scientific motivation, the experimental setup, and progress on the analysis
for obtaining the resonance strengths and energies. I will also discuss potential future
plans for additional measurements of the $^{18}$O(α, γ)$^{22}$Ne reaction with DRAGON.

Speaker: Dhruval Shah (McMaster University)

6:37 p.m. Target Fragmentation in Hadron Therapy: direct and inverse kinematic measurements

Particle therapy with protons and heavy ions relies on a precise understanding of nuclear interactions in tissue. In this context, nuclear fragmentation processes, in particular target and beam fragmentations, play a crucial role, producing secondary fragments with high linear energy transfer and impacting dose deposition and radiobiological effectiveness. However, at present fragmentation cross sections in the therapeutic energy range remain insufficiently constrained.

The FOOT (FragmentatiOn Of Target) experiment is designed to perform high-precision measurements of nuclear fragmentation cross sections in the 50-700 MeV/n energy range, with a target uncertainty of ~5%. Using inverse kinematics with 16O and 12C beams on C and C2​H4​ targets, FOOT investigates reaction mechanisms and fragment production over a broad charge range. This approach overcomes the intrinsic limitation of direct kinematics, where low-energy target fragments typically stop within the target material and remain experimentally inaccessible. First results obtained with 200 and 400 MeV/n 16O beams will be presented.

The possibility of performing the first direct measurement of target fragmentation induced by proton beams is being explored by the DAMON (Direct meAsureMent of target fragmentatiON) project, which has been funded by the European Union - Next Generation EU, Mission 4 Component 1, CUP H53D23001090006. DAMON employs Nano-Imaging Trackers (NITs), based on ultra-fine nuclear emulsion films with nanometric AgBr crystals, which provide sub-micrometre spatial resolution. This enables the reconstruction of short tracks from low-energy recoils and target fragments directly at the production point, without relying on kinematic boosting. The direct kinematics configuration is essential to access the genuine topology and phase space of proton-induced target fragmentation, providing observables that are otherwise inaccessible and offering a fully complementary perspective to inverse kinematics measurements. Exposures have been performed with proton beams in the 70-211 MeV range at several facilities: Trento Proton Therapy Center (Trento, Italy), CNAO (Pavia, Italy), HIMAC (Chiba, Japan) and the Nagoya Proton Therapy Center (Nagoya, Japan). The first results demonstrate the potential of NIT technology for precision studies of proton-induced nuclear fragmentation.

Results from both experiments provide new constraints on reaction channels and fragment yields in light-ion interactions with tissue-equivalent materials, contributing to a more accurate description of nuclear processes at therapeutic energies and offering relevant input for both nuclear reaction modelling and applied nuclear physics.

Speaker: Giuliana Galati (Università di Bari Aldo Moro & INFN Bari)

6:38 p.m. Fusion-evaporation Cross-section Measurements Near 56Ni Using TIP and TIGRESS at TRIUMF

The study of exotic, short-lived nuclei far from the valley of stability is crucial for the exploration of nuclear structure and nucleosynthesis. To fulfill these pursuits, fusion-evaporation reactions serve as an essential reaction mechanism for accessing exotic nuclei such as those near the proton drip line. However, the tools available for predicting fusion-evaporation reaction cross-sections --- and thus making accurate reaction rate predictions for new experiments --- have been found to overestimate by an order of magnitude. To address this, fusion-evaporation cross-section measurements are being made via comparison against observed gamma-ray peaks from Coulomb excitation.

This presentation will begin by introducing an experiment conducted at TRIUMF, Canada's particle accelerator centre, which used: the TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer (TIGRESS) for gamma-rays; the CsI Ball array in the TIGRESS Integrated Plunger (TIP) for charged particles; a calcium target with a thick gold backing; and a high-intensity stable beam of 20Ne to access the region near doubly magic 56Ni via 40Ca(20Ne,XaYp) reactions. The majority of the presentation will centre on the methodology used to measure fusion-evaporation cross-sections in the absence of a continuously-monitored beam intensity by combining the well-known Coulomb excitation formalism, theoretical fusion-evaporation angular distributions, and efficiency-corrected relative gamma-ray intensities. Results will be presented and discussed.

Speaker: Heinz Asch (Simon Fraser University)

6:39 p.m. Coupling of TIGRESS and EMMA with Auxiliary Array TIP at TRIUMF

Work has been conducted at TRIUMF, Canada's particle accelerator centre, to combine the capabilities of the TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer (TIGRESS) for gamma-rays, the CsI Ball array in the TIGRESS Integrated Plunger (TIP) for charged particles, and the ElectroMagnetic Mass Analyzer (EMMA) for recoil-mass spectrometry. This trio allows for an entirely new suite of measurements using fusion-evaporation, radiative-capture, and transfer reactions. This presentation will discuss the selectivity achieved by coupling TIGRESS and EMMA alongside a suite of auxiliary detectors housed within TIGRESS such as TIP. This combination of apparatus opens up a range of new studies into nuclear structure and astrophysics by enabling high-energy-resolution gamma-ray spectroscopy and reaction measurements of weak fusion-evaporation channels in the presence of dominant background reactions. The combined capabilities of TIGRESS, EMMA, and TIP in the context of a fusion-evaporation study of the region near doubly magic 56Ni without the requirement of neutron spectroscopy will be the core topic discussed.

Speaker: Heinz Asch (Simon Fraser University)

6:40 p.m. Characterization of high-spin states in neutron-rich Au isotopes near N=126: Regularities and inheritances

The interplay between single-particle and collective degrees of freedom in atomic nuclei constitutes a fundamental aspect in quantum many-body physics, particularly manifest in odd-nucleon systems where unpaired nucleons couple to the even-even core. The region southwest of 208Pb offers a rich landscape for such studies. For example, across the Au isotopic chain, isomeric bands based on πh11/2 and πh11/2 ⊗ νi13/2 configurations in odd-even and odd-odd Au, respectively, provide a systematic probe of how high-j unique-parity nucleons couple to the core. However, neutron-rich Au isotopes approaching N = 126 remain largely unexplored, where decoupling or weak-coupling limits are expected. Investigating the high-spin structure of these nuclei is therefore of considerable interest. Furthermore, detailed spectroscopic knowledge in this region is valuable for astrophysical r-process calculations, particularly for constraining first-forbidden β-decay rates.
Producing neutron-rich nuclei in this region and achieving unambiguous particle identification pose significant experimental challenges. To address the difficulties, MNT reactions between a 136Xe beam (7 MeV/u) and a 198Pt target were employed at GANIL, combined with a suite of complementary spectrometers. Projectile-like fragments (PLFs) were fully identified using the VAMOS++ spectrometer, and the corresponding target-like fragments (TLFs) near N ≈ 126 were selected based on isotopically identified PLFs and reconstructed excitation energies. Prompt γ rays were detected with AGATA, a state-of-the-art HPGe tracking array, enabling high-spin spectroscopy of the TLFs. Additionally, CATLIFE—a time-of-flight spectrometer coupled with the EXOGAM HPGe array—was employed to measure delayed γ rays and determine TLF mass numbers prior to neutron evaporation, providing crucial independent fragment characterization. A novel kinetic-energy calibration method based on supervised machine-learning techniques was implemented for the VAMOS++ data, improving ion charge-state identification at energies near the Bragg peak.
In this contribution, we will report new results on the high-spin structure of 195-202Au isotopes. New level schemes have been constructed and known structures extended above the long-lived isomers. Notably, new (25/2⁺) isomers in 199Au and 201Au have been identified, with half-lives of T1/2 = 140(20) μs and 15.2(29) μs, respectively. The excitation energies in the Au isotopes reflect structures inherited from corresponding states of the neighboring Hg cores and evolve consistently across the extended isotopic chain. A local dip in the level-energy systematics, deviating from the monotonic trend toward the N = 126 shell closure, is observed at N = 119. Furthermore, our measurements reveal the disappearance of the odd-J mirror bands in the level schemes of odd-odd Au isotopes for N ≥ 117. These experimental findings, interpreted within the framework of large-scale shell-model calculations, advance our understanding of the interplay between high-j orbitals and the collective core near the N = 126 shell closure.

Speaker: Youngju Cho (Argonne National Laboratory)

6:41 p.m. Developments for nuclear structure studies of heavy nuclides using the mass spectrometer SHIPTRAP

Super-heavy elements (Z > 103) owe their existence to nuclear shell effects and deformations of the nucleus, which stabilize the nucleus against Coulomb repulsion [1]. Direct mass measurements of isotopic and isobaric chains of these nuclides using Penning traps [2] can quantify the strength of these nuclear shell effects, allowing us to map nuclear shell evolution. Additionally, precise mass measurements can complement decay spectroscopy studies by measuring the excitation energy of low-lying, long-lived isomeric states.
The SHIPTRAP experiment studies transuranic nuclei produced via fusion-evaporation reactions at rates below one particle per hour. These measurements are possible thanks to technical developments carried out in the last few years such as a cryogenic buffer-gas stopping cell and the high-precision phase-imaging ion-cyclotron-resonance technique. These have already enabled the study of exotic nuclides with production cross sections on the order of 10 nb with SHIPTRAP [3]. To complement previous measurements, mass measurements of long-lived isotopes in Cm-Fm region can contribute to asses the size of the deformed neutron shell gap at N=152 as a function of the proton number. These can be accessed using a recoil ion source.
In this contribution, the development of a new recoil-ion source branch for SHIPTRAP, dedicated to the offline study of long-lived isotopes will be discussed. It consists of a compact gas cell that uses nonlinear electric fields to stop and transport recoil ions, coupled to a cooler-buncher RFQ to provide cooled ions for Penning trap mass spectrometry.

[1] O.R. Smits et al, Nat. Rev. Phys. 6, 86-98 (2024)
[2] M. Block, Nucl. Phys. A 944 471-491 (2015)

[3] O. Kaleja et al, Phys. Rev. C 106 054325 (2022)

Speaker: Briain Hartigan (JGU Mainz)

6:42 p.m. Precision mass measurement of barium isotopes and implications for double beta decay

Double $\beta$ (2$\beta$) and double electron capture (ECEC) decays are active areas of research, and confirmation of a neutrinoless decay channel would identify the neutrino as a Majorana particle. The half-lives of these decay modes depend sensitively on the masses of the parent and daughter isotopes as the Q-value determines both the resonant enhancement of neutrinoless ECEC decays [1] and the available phase space in standard ECEC decays [2]. Many candidate isotopes for such decays have yet to be observed experimentally.

We measured the nuclear masses of $^{132}$Ba and $^{134}$Ba with the JYFLTRAP double Penning trap mass spectrometer via the Phase Imaging Ion Cyclotron Resonance (PI-ICR) technique. Stable barium ions were produced using a plasma discharge ion source, mass-separated with a magnetic dipole, and then bunched in the radio-frequency quadrupole trap (RFQ) before injection into JYFLTRAP. We present a mass measurement of a double electron capture (ECEC) decay candidate ($^{132}$Ba) and discuss its relevance to the resonantly enhanced neutrinoless ECEC decay mode, as well as an updated calculation of the available phase space in two-neutrino ECEC decay.

References:
[1] K. Blaum, et al., Neutrinoless double-electron capture. Rev. Mod. Phys. 92(4), 045007 (2020)
[2] J. Kotila, F. Iachello, Phase space factors for β$^+$β$^+$ decay and competing modes of double-β decay. Phys. Rev. C 87(2), 024313 (2013)

Speaker: Brian Kootte

6:43 p.m. Study of key $^{57}$Ni(p,$\gamma$)$^{58}$Cu resonances and their impact on nucleosynthesis in supernovae

The $^{57}$Ni(p,$\gamma$)$^{58}$Cu reaction rate significantly impacts nucleosynthesis in various astrophysical sites. Perhaps most importantly, it impacts the production of the observable isotope $^{44}$Ti in core-collapse supernovae (CCSNe). Despite the importance of this reaction, no experimental rate previously existed for $^{57}$Ni(p,$\gamma$)$^{58}$Cu. To experimentally constrain this rate, the structure of $^{58}$Cu was probed via the $^{58}$Ni($^3$He,t)$^{58}$Cu reaction using two complementary measurements. The first measurement utilized GODDESS (GRETINA ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory’s ATLAS facility, and the second measurement utilized the Enge split-pole spectrograph at the University of Notre Dame’s Nuclear Science Laboratory. These measurements precisely determined level energies of $^{58}$Cu and constrained the level spins. The structure information provided by these measurements was used to arrive at the first experimentally constrained rate for $^{57}$Ni(p,$\gamma$)$^{58}$Cu, and the impact of this newly-constrained rate on the production of $^{44}$Ti in CCSNe was investigated via nuclear network calculations. Experimental procedures, analysis, and results will be presented.

This work is supported by the University of Notre Dame, U.S. Department of Energy (DOE), National Science Foundation, National Nuclear Security Administration, and DOE Office of Science Graduate Student Research program. This work used the resources of Argonne National Laboratory's ATLAS facility.

Speaker: Scott Carmichael (Argonne National Laboratory)

6:44 p.m. Coupled Alpha/Beta/Gamma Detection at SFU with SCI-CASTER and the 8Pi Spectrometer

The Simon Fraser University Nuclear Science Laboratory (NSL) is home to the SCI-CASTER project, which aims to develop position-sensitive ionization chamber detector technologies for precision charged particle measurements. Modern waveform digitization and analysis methods enable this by allowing for the direct application of the Shockley-Ramo theorem to the induced charge signals of the ionization chamber, yielding measurements of charge drift times and track proximity to detector electrodes.
Additionally, refurbishment of the 8Pi gamma-ray spectrometer array has been underway at the NSL to bring all 132 inner-layer Bismuth Germanium Oxide (BGO) scintillator detectors and 20 outer-layer Compton-Suppressed Spectrometers (CSS) to full operation with modern amplification, high-voltage, and data acquisition hardware. To date, the BGO inner-layer has been brought to full performance.
The combination of a SCI-CASTER detector with the 8Pi spectrometer will in principle allow coupled alpha/beta/gamma spectroscopy to be carried out at SFU, resulting in the full characterization of long-lived isotope decay chains and enhancing minute sample contamination detection through the application of high-efficiency and high-precision data acquisition. The in-progress design of the proposed SCI-CASTER detector will be presented, alongside intermediate results of the simulation and prototype testing phases of the project.

Speaker: Andrew Redey (Simon Fraser University)

6:45 p.m. Benchmarking Interaction Ordering in GRETINA Using Doppler-Corrected Energies and Linear Polarization

Accurate identification of γ-ray interaction sequences in highly segmented HPGe detector arrays is critical for extracting nuclear structure observables. In particular, the determination of the first and second interaction points directly impacts Doppler correction and linear polarization measurements. However, ambiguities in interaction ordering remain a key limitation in current analysis approaches.

We present a framework for benchmarking interaction ordering in the GRETINA array using physics-driven observables. Doppler-corrected γ-ray energy resolution is used as a diagnostic for the accuracy of first interaction point identification, while linear polarization sensitivity provides a complementary probe of second interaction point reconstruction.

Initial studies demonstrate that these observables provide stringent and independent constraints on interaction ordering, enabling quantitative comparison between reconstruction approaches. This methodology establishes a direct link between detector-level reconstruction and experimentally accessible physics quantities.

These benchmarks provide a pathway for systematically improving interaction ordering and extending the sensitivity of γ-ray spectroscopy measurements, particularly for weak transitions and polarization observables in complex datasets.

Speaker: Nick Coldiron (University of Massachusetts Lowell)

6:46 p.m. Probing transitional structure and collectivity in neutron-deficient 158Er

The rare-earth region provides an ideal testing ground for nuclear structure evolution, where enhanced collectivity and low-lying 0⁺ states challenge simple models and require additional degrees of freedom such as triaxial and octupole deformation. Much of the existing experimental data, however, is concentrated in the stable Nd–Dy region, and it remains unclear whether these models can be extended to higher proton numbers.
Neutron-deficient erbium isotopes provide access to the N∼90 transitional region at higher proton numbers, where experimental data are scarce and theoretical descriptions remain largely untested. In this region, while the ground-state band evolves smoothly toward the N=82 shell closure, the excited 0⁺ band exhibits a minimum in energy at N=90, indicating a change in structure and possible mixing of different configurations across ^156,158,160Er.
A Coulomb-excitation experiment has been performed at TRIUMF using a radioactive ¹⁵⁸Er beam with γ rays detected by TIGRESS. Combined with complementary new data from β-decay, the analysis aims to extract precise E2 matrix elements between the ground state band and the K = 0,2 bands of 158Er, to distinguish between collective and quasiparticle excitations, constrain band structure and possible triaxiality, and determine model-independent shape parameters using Kumar–Cline sum rules. GOSIA analysis is in progress, and preliminary results provide insight into the structure and collectivity of ¹⁵⁸Er.

Speaker: Yiyi Zhu

6:47 p.m. Development of an Ion Transport and Identification System for Barium Tagging in Liquid Xenon Neutrinoless Double Beta Decay Experiments

Neutrinoless double beta decay ($0\nu\beta\beta$) is a hypothetical, lepton-number-violating process which, if observed, would confirm the Majorana nature of the neutrino. A proposed next-generation experiment searching for this decay in liquid xenon (LXe) is nEXO, anticipated to deploy 5 tonnes of LXe enriched to 90% in the double beta decay ($2\nu\beta\beta$) isotope $^{136}$Xe, targeting a half-life sensitivity beyond 10$^{28}$ years. A unique possibility with experiments such as nEXO is the possibility to access the detector volume to probe for the presence of the $^{136}$Ba daughter produced in a candidate decay. This technique, referred to as barium tagging, will provide confirmation of $0\nu\beta\beta$ on an event-by-event basis, reducing backgrounds down to the Standard Model-allowed $2\nu\beta\beta$ channel.

We present a summary of the Ba-tagging scheme being initially developed as an upgrade path for the nEXO experiment, with a focus on the development of the ion extraction and identification system. The system includes an RF-only ion funnel for transporting the Ba$^+$ from a high-pressure xenon gas environment to vacuum environment where it can then be trapped. The trapped Ba$^+$ can subsequently be identified via laser fluorescence spectroscopy. The system also includes a multiple-reflection time-of-flight mass spectrometer to confirm the presence of $^{136}$Ba$^+$ and enable systematic studies of ion extraction and transport using other ion species.

We will describe the overall tagging scheme and operating principles, the status of the R&D efforts and the near-term goals towards realizing a complete demonstration of single-ion extraction from LXe. These efforts aim to benchmark the overall performance of this Ba-tagging scheme and quantify the overall gain in discovery reach through its implementation in next-generation liquid xenon neutrinoless double beta decay searches.

Speaker: Hussain Rasiwala (McGill University)

6:48 p.m. In-source laser spectroscopy of ground- and isomeric states of neutron-rich polonium with LIST

The Isotope Separator On Line DEvice (ISOLDE) is a facility for the production and study of radioactive ion beams at CERN. The Laser Ion Source and Trap (LIST) of the Resonance Ionization Laser Ion Source (RILIS) enables access to isotopes that otherwise suffer from strong isobaric contamination [1,2].
We report the continued study of neutron-rich polonium ($Z=84$) isotopes through in-source laser spectroscopy with LIST, where improved suppression of isobaric francium contamination enabled extension of measurements up to $^\text{220}\text{Po}$. Alpha-decay spectra were recorded with the ISOLDE Decay Station (IDS) with sufficient resolution to distinguish between polonium ground and isomeric states as well as isobaric contaminants.
From isotope shifts and hyperfine structure in atomic transitions, the changes in mean-squared charge radii $\langle r^2 \rangle$ and the magnetic dipole and electric quadrupole moments of $^{219,220}\text{Po}$ ground states and the high-spin isomers $^{\text{211m,212m}}\text{Po}$ were extracted for the first time. For $^\text{204,206-211,217,218}\text{Po}$, the obtained values agree with literature [2-6]. Comparison to single-particle and empirical moments calculated with the additivity relation suggests a marked difference in $\nu1i_{11/2}$ occupation between the isomeric and ground states of $^{211,212}\text{Po}$. According to several DFT calculations [7,8], occupation of this orbital determines the kink in the $\langle r^2 \rangle$ at $N=126$.
The LIST furthermore enabled the first detailed spectroscopy of $^{219,220}\text{Po}$ with IDS and the Alpha SETup (ASET), and a summary will be presented.

[1] D. Fink et al., Nucl. Instrum. Methods Phys. Res. B 344, 83 (2015)
[2] D. A. Fink et al., Phys. Rev. X 5, 011 018 (2015)
[3] D. Kowalewska et al., Nucl. Shapes Struct. Low Excit. Energies, 93 (1992)
[4] M. Seliverstov et al., Phys. Lett. B 719, 362 (2013)
[5] T. E. Cocolios et al., Phys. Rev. Lett. 106, 052 503 (2011)
[6] M. Seliverstov et al., Phys. Rev. C 89, 034 323 (2014)
[7] P. M. Goddard et al., Phys. Rev. Lett. 110, 032 503 (2013)
[8] U. C. Perera and A. V. Afanasjev, Phys. Rev. C 107, 064 321 (2023)

Speaker: Julius Wessolek (TRIUMF)

6:49 p.m. Towards a Revised Picture of Octupole Structure in Neutron-Rich $^{148}$Ba

Octupole deformation in Barium isotopes has been experimentally established up to $N$=90 [1,2], with more recent evidence extending this behavior up to $N$=94. Symmetry-conserving configuration mixing (SCCM) calculations confirm an evolution toward increasingly quadrupole-deformed shapes accompanied by sustained octupole correlations in this region[3].

New spectroscopic information was obtained using the GRIFFIN spectrometer on neutron-rich $^{148}$Ba isotope following the $\beta$-decay from $^{148}$Cs. Particular attention is given to a tentative $(3-)$ state, whose structure is re-examined in light of the new data. The observed decay patterns suggest that this assignment may involve a more complex configuration, potentially reflecting mixing between states of different character. Additionally, gamma-ray transitions are investigated with the aim to further refine the level scheme.

Ongoing analysis aims to clarify the nature of this state and its role in the emerging picture of octupole collectivity. The results are discussed in the context of isotopic and isotonic systematics, providing insight into the evolution of quadrupole deformation and octupole correlations in this mass region.

References

[1] B. Bucher et al., Phys. Rev. Lett. 116, 112503 (2016)

[2] B. Bucher et al., Phys. Rev. Lett. 118, 152504 (2017)

[3] R. Lică et al., Phys. Rev. C 97, 024305 (2018)

Speaker: Silvia Murillo Morales (TRIUMF)

6:50 p.m. Precision Mass Measurements of Neutron-Rich Sb Isotopes and Structure Evolution Beyond N=82

The neutron-rich Sb isotopes beyond the N=82 shell closure provide a sensitive testing ground for nuclear structure far from stability. Precision mass measurements in this region are key inputs for studying neutron pairing, the evolution of two-neutron separation energies, and the possible emergence of a subshell closure at N≈90.
The Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) at TITAN-TRIUMF is particularly well suited for accessing such short-lived and weakly produced isotopes. Its fast measurement cycles, high resolving power, and sensitivity enable measurements on the millisecond timescale at yields well below one ion per second, while simultaneously suppressing isobaric contaminants.
In this work, we report mass measurements of neutron-rich $^{136-140}$Sb performed with the TITAN MR-TOF-MS, including first-time measurements of $^{139-140}$Sb. These results offer new insights into nuclear structure beyond N=82.

Speaker: Pavithra Weligampola (TRIUMF)

Wed, July 29

9:00 a.m. → 10:30 a.m. Wednesday Early Morning Block: (Chair: Heather Crawford)

9:00 a.m. Shaking up the Periodic Table with Superheavy Element Molecules

The Periodic Table is a cornerstone of chemistry, but its validity is challenged by the extreme properties of superheavy elements (SHEs, Z ≥ 104) and actinides (Z > 88). Relativistic effects, stemming from their large nuclear masses, significantly alter their chemical behaviors, potentially limiting the predictive power of the Periodic Table. Recent breakthroughs have provided insights into the chemistry of these elements, including the direct identification of molecular species formed by actinium (Ac, Z = 89) and nobelium (No, Z = 102) ions. Using a cutting-edge, atom-at-a-time technique at the 88-Inch Cyclotron Facility at Lawrence Berkeley National Laboratory, we have synthesized and characterized molecular species produced by these ions in reactions with H2O and N2. Our findings underscore the importance of direct identification of molecules in SHE chemistry experiments and offer new perspectives on the chemical properties of these enigmatic elements. This presentation will explore the current state of superheavy element chemistry research, highlighting recent advances and future directions for unraveling the mysteries of SHE chemistry. By pushing the boundaries of our understanding, we aim to shed light on the chemical behaviors of these extraordinary elements and challenge our current understanding of the Periodic Table.

Speaker: Jennifer Pore (Lawrence Berkeley National Laboratory)

9:30 a.m. Hyperfine spectroscopy of the $K=8^-$ isomer in $^{254}$No with JetRIS resolving a 20-year-old debate

Modern nuclear structure studies in the heavy-element region combine state-of-the-art experimental techniques with advanced theoretical models [1,2]. This interplay between experiment and theory not only enhances the interpretation of experimental data but also drives the refinement of theoretical approaches, underscoring the importance of benchmarking models against independent experimental observables.

The $K^\pi=8^-$ state in $^{254}$No has been investigated extensively over the past two decades [3-5], yet its configuration remained unresolved. Owing to the production mechanisms employed in previous studies, which do not populate the rotational band built on the isomer, in-beam and decay spectroscopy measurements have not been sufficient to determine its $g$-factor, precluding a definitive configuration assignment. Consequently, both neutron–neutron [4] and proton–proton [3,5] two-quasiparticle configurations have been proposed based on indirect evidence, such as decay patterns and comparisons between measured excitation energies and theoretical predictions.

In this work, we resolve this ambiguity by presenting nuclear model-independent measurements of the electromagnetic multipole moments of the $K^\pi=8^-$ state in $^{254}$No. Using the in-gas-jet laser ionisation spectroscopy setup JetRIS [6,7], we have recorded the hyperfine spectrum of the short-lived isomer ($T_{1/2}={259(7)}~{ms}$ [5]), enabling the extraction of its $g$-factor. In addition, we provide information on the quadrupole deformation of the isomer and on the change in mean-square charge radius between the ground and excited states of $^{254}$No.

Previous studies in the $N=150$ region have identified and characterised $K^\pi=8^-$ states in $^{244}$Pu, $^{246}$Cm, $^{250}$Fm, and $^{252}$No, all consistently assigned a neutron–neutron two-quasiparticle configuration [8,9]. Our results for $^{254}$No demonstrate that this structure persists across the $N=152$ sub-shell gap, challenging the predictions of most theoretical models.

[1] M. Block et al. Prog. Part. Nucl. Phys., 116, 2021.
[2] J. Dobaczewski et al. Nucl. Phys. A, 944, 2015.
[3] R-D Herzberg et al. Nature, 442(7105), 2006.
[4] R.M. Clark et al. Phys. Lett. B, 690(1), 2010.
[5] S. G. Wahid et al. Phys. Rev. C, 111, 2025.
[6] S. Raeder et al. Nucl. Instrum. Methods Phys. Res. B, 463, 2020.
[7] J. Lantis et al. Phys. Rev. Res., 6, 2024.
[8] F.P. Heßberger. arXiv:2309.10468, 2023.
[9] F.G. Kondev et al. Atomic Data and Nuclear Data Tables, 103-104,2015.

Speaker: Fedor Ivandikov (KU Leuven)

9:50 a.m. Laser spectroscopy of heavy actinides

The heaviest elements are of interest to nuclear and atomic physicists due to their peculiar properties. While nuclear shell structure effects are responsible for their very existence stabilizing them against spontaneous disintegration, the structure of their electronic shells is affected by strong relativistic effects leading to different atomic and chemical properties compared to their lighter homologs. The atomic structure can be probed by laser spectroscopy. This is a powerful tool to unveil fundamental atomic and, by detecting subtle changes in atomic transitions, nuclear properties. The scarcity in atomic information on the heavy element of interest, the limited availability, and the rather short half-lives make experimental investigations challenging and demand very sensitive experimental techniques.
Here, laser spectroscopic studies of accelerator produced heavy nuclei were performed using the RADRIS (RAdiation Detected Resonance Ionization Spectroscopy) setup for laser spectroscopy inside a buffer gas cell. This sensitive technique enabled laser spectroscopy measurements on isotopes of nobelium (No, $Z=102$), fermium (Fm, $Z=100$) and californium (Cf, $Z=98$), which were produced with atom-at-a-time quantities in fusion-evaporation reactions at the velocity filter SHIP at GSI, Darmstadt.
Complementary hot-cavity laser spectroscopy on radio-chemically purified samples allowed for off-line investigation of long-lived, reactor-bred isotopes of the heavy actinides curium (Cm, $Z=96$), californium, einsteinium (Es, $Z=99$), and fermium. This experimental work is accompanied by improvements of theoretical atomic calculations enabling the determination of nuclear ground state properties from the extracted atomic observables of isotope shifts and hyperfine structure parameters. This provides insight to the peculiar nuclear nature and, in particular, the deformation of the heaviest elements. The obtained results will be discussed in view of nuclear theory predictions together with perspectives for laser spectroscopic investigations in even heavier elements.

Speaker: Sebastian Raeder

10:10 a.m. In-beam $\gamma$-ray spectroscopy of $^{249,251}$Md

In-beam γ-ray spectroscopy experiments on the heavy odd-Z nuclei $^{249}$Md and $^{251}$Md were performed at the ATLAS accelerator facility of Argonne National Laboratory using the $^{203}$Tl($^{48}$Ca, 2n) and $^{205}$Tl($^{48}$Ca, 2n) fusion evaporation reactions, respectively. In both experiments the Argonne Gas-Filled Analyzer (AGFA) was used to separate recoils of interest, while Gammasphere detected prompt γ-rays emitted from excited states and the X-array provided sensitivity to isomeric states and decays. Recoil- and recoil-decay tagging techniques were utilised to identify new rotational bands in $^{249}$Md based on one-proton quasiparticle states. One observed set of states forms a pair of strongly coupled bands with relatively strong E2 transitions, and another sequence of γ-ray transitions is indicative of a decoupled band of E2 transitions. These bands are respectively assigned as based on the Nilsson level configurations 7/2$^{−}$[514] and 1/2$^{−}$[521], corresponding to the ground and first excited state of $^{249}$Md. The presence of at least one high-$K$ multi-quasiparticle isomer was also confirmed in $^{249}$Md. This talk presents the results of the $^{249}$Md experiment, and a discussion of preliminary findings from the experiment on $^{251}$Md.

This work was supported, in part, by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-05CH11231 (LBNL), Contract No. DE-AC02-98CH10886 (BNL). This work is funded by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 (ANL). This research used resources of Argonne National Laboratory’s ATLAS facility, which is a DOE Office of Science User Facility.

Speaker: Corrigan Appleton (LBNL)

10:30 a.m. → 11:00 a.m. Coffee break

11:00 a.m. → 12:30 p.m. Wednesday Morning Late Session Block: (Chair: Liss Vazquez Rodriguez)

11:00 a.m. ACTAR TPC Studies of Direct and Resonant Reactions: Insights from the TRIUMF campaign

The ACtive TARget and Time Projection Chamber (ACTAR TPC), is a versatile detector designed to address a wide range of nuclear physics topics near the drip-lines. In this contribution, previous results obtained with ACTAR TPC in transfer reaction studies with a 20O beam will be reviewed, demonstrating its capabilities for precise measurements in inverse kinematics. Particular emphasis will be placed on preliminary results from an experimental campaign carried out at TRIUMF in 2025. Nuclear structure studies of neutron-rich Li isotopes and proton-rich exotic nuclei will be presented. These results underline the potential of ACTAR TPC as a powerful tool for studying direct and resonant reactions with rare isotope beams.

Speaker: Beatriz Fernandez Dominguez (University of Santiago de Compostela)

11:30 a.m. Determination of the electromagnetic nature of the Low Energy Enhancement in the γ-ray strength function of 70Zn

The γ-ray strength function ($\gamma$SF) is a statistical nuclear property that describes the likelihood of $\gamma$-ray emission as a function of $\gamma$-ray energy. Investigations into the $\gamma$SF have identified prominent features in its shape, such as the giant dipole resonance, pygmy dipole resonance, scissors mode, and low energy enhancement (LEE). The LEE is a fundamental property of atomic nuclei, and it has been shown to have significant impact on astrophysical reaction rates [1]. The electromagnetic nature of the LEE has puzzled the nuclear physics community since it was first discovered in $^{56,57}$Fe [2], and despite two decades of theoretical and experimental efforts, it remains unclear if the LEE is due to electric dipole or magnetic dipole transitions [3]. Here, we present the results from an experiment conducted at the Facility for Rare Isotope Beams (FRIB) at Michigan State University, where we use a novel combination of experimental and analytical techniques to probe the electromagnetic nature of the LEE in the nucleus $^{70}$Zn. At FRIB, beams of the ground and second isomeric states of 70Cu (J$^π$=6$^-$ and J$^π$=1$^+$, respectively) were isolated with the Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer [4] and delivered to the upgraded Summing NaI(Tl) Total Absorption Spectrometer [5]. These two $\beta$-decaying states populate different levels in $^{70}$Zn, with the 6$^-$ ground state favoring E1+M1 transitions and the 1$^+$ isomeric state favoring M1 transitions. In this contribution, we present the comparison of the $^{70}$Zn γSF extracted from both $\beta$-decaying states of $^{70}$Cu with the $\beta$-Oslo [6] and Shape [7] methods. From these results we are able to make a conclusive determination about the electromagnetic nature of the LEE in $^{70}$Zn.

[1] Larsen, A. C. and Goriely, S. Impact of a low-energy enhancement in the γ-ray strength function on the neutron-capture cross section. Phys. Rev. C, 82, 014318 (2010).
[2] Voinov, A. et al. Large enhancement of radiative strength for soft transitions in the Quasicontinuum. Phys. Rev. Lett. 93, 142504 (2004).
[3] Midtbø, J. E. et al. Consolidating the concept of low-energy magnetic dipole decay radiation. Phys. Rev. C. 98 064321 (2018).
[4] Ringle, R., Schwarz, S. and Bollen, G. Penning trap mass spectrometry of rare isotopes produced via projectile fragmentation at the LEBIT facility. Int. J. Mass Spectrom. 349-350 87-93 (2013).
[5] Ronning, E. K. et al. The upgraded summing NaI(Tl) (SuN++) absorption spectrometer. Nucl. Inst. and Meth. in Phys. Res. A, 1082 170930 (2026).
[6] Spryou, A. et al. Novel technique for Constraining r-Process (n,γ) Reaction Rates. Phys. Rev. Lett. 113 232502 (2014).
[7] Wiedeking, M. et al. Independent normalization for γ-ray strength functions: the shape method. Phys. Rev. C, 104 014311 (2021).

Speaker: Eleanor Ronning (INFN Padova)

11:50 a.m. Charge Radii of 52,53Ni from Precision Laser Spectroscopy

The evolution of nuclear structure in the magic nickel chain provides stringent tests of nuclear theory with the presence of three doubly magic nuclei ($^{48,56,78}$Ni) and a prominent subshell closure at $^{64}$Ni. In this work, precision laser spectroscopy measurements on $^{52,53}$ Ni will be presented, which extend the known Ni charge-radii chain beyond doubly magic $^{56}$Ni towards the proton drip line at $^{48}$Ni. The nuclear magnetic-dipole and electric-quadrupole moments of $^{53}$Ni will also be reported. From the difference in the $^{52}$Ni-$^{52}$Cr mirror pair charge-radii, a constraint on the slope parameter (L) in the symmetry energy of the nuclear equation of state will be deduced, analogous to the previously measured $^{54}$Ni-$^{54}$Fe mirror pair [1]. Details of the measurement technique and results will be discussed.

[1] S. V. Pineda, et. Al., Phys. Rev. Lett. 127 (2021) 182503
This work is supported in part by National Science Foundation Grant No. PHY-21-11185 and US Department of Energy, Office of Science Grant No. DE-SC0000661.

Speaker: Adam Dockery (Michigan State University / Facility for Rare Isotope Beams)

12:10 p.m. Support for multiple shape coexistence: the first lifetime measurements of the $0^+_3$ states in $^{118}$Sn and $^{120}$Sn

The semi-magic Sn nuclei, extending beyond the $N=50$ and $N=82$ shell closures, present one of the most-studied isotopic chains on the nuclear chart. $^{118}_{50}$Sn$_{68}$ and $^{120}_{50}$Sn$_{70}$ lie in the neutron mid-shell, where shape coexistence was proposed with the signature of deformed excited $0^+$ states intruding into the seniority-like spherical yrast bands. However, transition strengths studies were hindered because only limits were available in the literature on the lifetimes of the excited $0^+_3$ states. Notably, the lack of electric monopole strengths between the $0^+_3$ and $0^+_2$ states, $\rho^2(E0;0^+_3\rightarrow0^+_2)$, obscured the shape difference and mixing amplitudes between the excited $0^+$ states.

These $0^+_3$ lifetimes were recently measured for the first time in a thermal-neutron capture experiment at the Institut Laue-Langevin. The world's highest-flux thermal neutron beam of $10^8$~neutrons/cm$^2$/s was delivered onto enriched $^{117}$Sn and $^{119}$Sn targets, respectively. Low-spin states in $^{118,120}$Sn were populated up to the $\approx 9$-MeV neutron separation energies, and the decaying gamma-ray cascades were detected with the Fission Product Prompt Gamma-ray Spectrometer (FIPPS) comprised of eight Compton-suppressed HPGe clovers coupled to an array of 15 LaBr$_3$ fast scintillation detectors.

In total, $\approx 4\times10^9$ counts were recorded in the $\gamma\gamma\gamma$ cube for each isotope, where two LaBr$_3$ events were in coincidence with one HPGe.

Monopole transition strengths from the lifetime measurements for the $0^+_3$ states in $^{118,120}$Sn will be presented along with theoretical interpretations employing MR-CDFT calculations without adjustable parameters.

Speaker: Frank (Tongan) Wu (Simon Fraser University)

12:30 p.m. → 2:00 p.m. Lunch

2:00 p.m. → 5:30 p.m. Free afternoon

Stroll through Gas Town, Stanley Park, or Granville Island

2:00 p.m. → 4:30 p.m. TRIUMF Tour (optional- registration needed)

Thu, July 30

9:00 a.m. → 10:30 a.m. Thursday Morning Early Session Block: (Chair: James Allmond)

9:00 a.m. Shape coexistence studied with Coulomb excitation and AGATA

The history of Coulomb-excitation measurements with the new-generation
European γ-ray spectrometer AGATA dates back to the very first physics experiment with this array, which took place in April 2010 and aimed at investigation of a highly-deformed structure in 42Ca [1]. The shape parameters obtained from this study confirm that the excited structure in 42Ca possesses a strikingly large elongation, similar to that established for superdeformed bands in this mass region, and a slightly non-axial character. In contrast, those for the ground state are consistent with large fluctuations about a spherical shape.

During the AGATA campaign at GANIL (2014-2021) Coulomb-excitation data were collected as a by-product of experiments performed at near-barrier beam energies. Notably, the analysis of slightly ”unsafe” Coulomb-excitation data on 106Cd, collected during an experiment aiming at lifetime measurements in 106,108Sn [2], provides information on the collectivity of the presumably oblate structure built on the 0+3 state, as well as on the role of octupole correlations in this nucleus [3, 4].

Coulomb-excitation experiments to study nuclear shapes constitute one
of the pillars of the on-going AGATA campaign at LNL (2022-2028). Their
main focus is on multiparticle-multihole excitations across the Z = 50 shell gap in Cd, Pd, and Te nuclei, although the structure of nuclei as light as 8Li and as heavy as 232Th has also been probed using this method. Another area of interest has been the region of light A ≈ 70 nuclei known for prolate-oblate shape coexistence.

I will discuss the highlights from Coulomb-excitation studies with AGATA, as well as preliminary results of selected experiments from the current campaign.

References
[1] K. Hady´nska-Kl¸ek et al., Phys. Rev. Lett. 117, 062501 (2016).
[2] M. Siciliano et al., Phys. Lett. B 806, 135474 (2020).
[3] D. Kalaydjieva, PhD thesis, Universit´e Paris-Saclay, 2023.
[4] D. Kalaydjieva, submitted to Eur. Phys. J. A (2026).

Speaker: Dr Magda Zielinska, (CEA Saclay)

9:30 a.m. Search for Shape Coexistence Signatures in 100Ru using Thermal Neutron Capture Reaction.

At the forefront of nuclear structure research is the topic of shape coexistence, which occurs when states within the same nucleus at similar energies possess distinct shapes. Studies of nuclei in the Zr (Z=40) - Sn (Z=50) region have shown evidence for shape coexistence with deformed rotational-like bands coexisting with spherical or weakly deformed ground state configurations. In the Ru (Z=44) isotopes, strong evidence has emerged for shape coexistence within 102Ru and 104Ru from Coulomb excitation [1,2], and it was suggested to be present in 98Ru and 100Ru as well [3]. In order to explore shape coexistence in 100Ru, and also probe possible vibrational motion, key mixing ratios and the observation of low-energy, and hence often very weak intensity, transitions between non-yrast states are required. The study of 100Ru presented in this work aims to extract precise transition multipolarity mixing ratios, unobserved weak g-ray transitions, and transition probabilities to resolve its structural nature. We used the thermal neutron capture reaction, 99Ru(n,g)100Ru, carried out at the Institut Laue-Langevin in Grenoble, France [4]. The g-ray transitions depopulating the excited states in 100Ru were detected by the FIPPS array consisting of two sets of eight clover-type hyper pure Germanium detectors. FIPPS provides high efficiency and the ability to perform detailed gamma-gamma angular correlations due to its high granularity. Results from the current analysis will be presented with an emphasis on the structural implications of the results.

Speaker: Sangeet Pannu (University Of Guelph)

9:50 a.m. Shape transitions of the 2+ states in 106,108,110Sn from Coulomb excitation

The experimental $B(E2; 2_1^+ \to 0_1^+)$ values in neutron-deficient, even-even Sn isotopes are found to be enhanced compared to calculations, a discrepancy which has eluded a satisfactory solution for over a decade. A Monte Carlo Shell Model (MCSM) [1] attributed this phenomenon to significant proton excitations across the $Z = 50$ shell in neutron-deficient Sn isotopes, and predicted a shape transition from a prolate to an oblate quadrupole deformation of the $2_1^+$ states from $^{106}$Sn to $^{110}$Sn.

A safe-energy Coulomb excitation campaign of $^{106,108,110}$Sn was conducted at HIE-ISOLDE, CERN. The radioactive Sn beams were accelerated to 4.4-4.5 MeV per nucleon and Coulomb excited on $^{206}$Pb targets. Gamma rays from the beam and the target nuclei were detected with the Miniball HPGe spectrometer [2]. In all three nuclei, record $\gamma$-ray counts were obtained from Coulomb excitation experiments [3].

Through excitation probability analysis in GOSIA [4,5], The $B(E2; 2_1^+ \to 0_1^+)$ value of $^{110}$Sn was determined with the best precision to date as 451(22) e$^2$fm$^4$, and the $B(E2; 4_1^+ \to 2_1^+)$ and $B(E2; 4_2^+ \to 2_1^+)$ values were also determined for the first time [6]. Furthermore, the spectroscopic quadrupole moment $(Q_s)$ of the $2_1^+$ state of $^{110}$Sn was newly determined as $+0.20(8)$ eb. Both the sign and the magnitude of $Q_s(2_1^+)$ are in agreement with the MCSM prediction of an oblate shape for the $2_1^+$ state in $^{110}$Sn [1]. Preliminary results suggest a negative $Q_s(2_1^+)$ for $^{106}$Sn and $Q_s(2_1^+) \sim 0$ for $^{108}$Sn, which are also consistent with MCSM. The shape transition in the light Sn isotopes will be discussed, as well as a more detailed view on the role of protons above the $Z = 50$ shell.

References:
[1] T. Togashi et al., Phys. Rev. Lett. 121, 052601 (2018).
[2] N. Warr et al., Eur. Phys. J. A 49, 40 (2013).
[3] J. Park et al., JPS Conf. Proc. 32, 010036 (2020).
[4] T. Czosnyka, D. Cline, and C. Y. Wu, Bull. Am. Phys. Soc. 28, 745 (1983).
[5] M. Zielinska et al., Eur. Phys. J. A 52, 99 (2016).
[6] J. Park et al., Phys. Rev. Lett. 135, 222502 (2025).

Speaker: Jason Park (Lund University/Hope College)

10:10 a.m. Investigating the deformation of intruder states in 79Zn via Coulomb excitation

In the region of N~50 several pieces of evidence supporting shape coexistence close to 78Ni have been found [1-3]. In particular, the ∼940-keV 1/2+ isomeric state in 79Zn, first observed in a (d,p) transfer measurement [4], has been interpreted as an intruder state, related to neutron excitations across N=50. Laser-spectroscopy measurements found a large isomeric shift for this state with respect to the 79Zn 9/2+ ground state indicating a significantly larger mean squared charge radius [2]. With the assumption of an axial quadrupole shape, this suggests a deformation of β=0.22, considerably larger than β=0.15 of the ground state. Indeed, the intruder structure in 79Zn has been attributed to a K=1/2 rotational band [3].

To probe the quadrupole collectivity of the 79Zn intruder states, we performed a Coulomb-excitation measurement with a post-accelerated 79Zn beam from HIE-ISOLDE that consisted of a mixture of nuclei in the 9/2+ ground state and the 1/2+ isomeric state, to populate excited states built on these two different configurations. In the experiment, γ rays were detected by the Miniball array [5], while scattered projectiles and beam recoils by an annular DSSD detector placed at forward angles.

The extracted quadrupole strengths from the Coulomb-excited transitions in the level scheme will be presented and compared with state-of-the-art shell model calculations. The implications of the results in the context of the shape coexistence around 78Ni will be discussed.

References
[1] A. Gottardo et al., Phys. Rev. Lett. 116, 182501 (2016)
[2] X. F. Yang et al., Phys. Rev. Lett. 116, 182502 (2016)
[3] L. Nies et al., Phys. Rev. Lett. 131, 222503 (2023)
[4] R. Orlandi et al., Phys. Lett. B 740, 298 (2015)
[5] N. Warr et al. ,Eur. Phys. J. A 49, 40 (2013)

Speaker: Filippo Angelini (GSI)

10:30 a.m. → 11:00 a.m. Coffee break

11:00 a.m. → 12:30 p.m. Thursday Morning Late Session Block: (Chair: Robert Grzywacz)

11:00 a.m. From Shell Evolution to Halo Structure: Quasi-Free Scattering at SAMURAI

Quasi-free scattering (QFS) reactions in inverse kinematics have emerged as a powerful tool to probe the microscopic structure of exotic nuclei. Using a thick liquid hydrogen target and the SAMURAI spectrometer at RIBF, a series of (p,2p) and (p,pn) measurements have been performed. Owing to the Fourier relationship between momentum and spatial distributions, the root-mean-square (rms) radii of valence nucleon orbitals can be extracted from measured momentum distributions following one-nucleon removal within the DWIA framework. In particular, the analysis of the $^{52}$Ca(p,pn)$^{51}$Ca reaction revealed an extended p$_{3/2}$ neutron orbital, which was suggested to be responsible for the unexpectedly large charge radii observed in neutron-rich Ca isotopes while preserving the double-magic character of $^{52}$Ca. Building on this approach, we extend this method to study neutron-halo systems, in which weakly bound valence neutrons exhibit spatially extended distributions. The Borromean nucleus $^{11}$Li, with the valence neutrons dominantly occupying the p and s orbitals, represents a prototypical two-neutron halo system. In contrast, $^{17}$B exhibits a surprisingly small s-wave component despite long being considered as a two-neutron halo nucleus. These observations were interpreted as challenging the conventional view that dominant s- or p-wave occupancy is a prerequisite for halo formation. In this talk, we present results on the extracted rms radii of valence neutron orbitals in $^{11}$Li and $^{17}$B using measured momentum distributions following the (p,pn) reactions. The results may provide new insights into the underlying mechanisms of halo formation.

Speaker: Hongna Liu (Beijing Normal University)

11:30 a.m. Neutron knockout from titanium isotopes near the new magic numbers N=32,34

The nuclear shell model is extremely effective in describing the behaviour of stable magic nuclei. Modern radioactive ion beam facilities have facilitated tests of the shell model along chains of magic isotopes stretching far from the valley of stability. With increased isospin asymmetry, the energies of proton and neutron orbitals can shift, in some cases moving far enough that magic numbers vanish or appear. Double-magicity of calcium isotopes has been established at conventionally non-magic $N=32,34$ on the basis of mass, radius, $E(2^+)$ and $B(E2)$. In the neighbouring elements, however, clear evidence for the persistence of these magic neutron numbers remains elusive, and more detailed spectroscopy is needed to understand how the neutron orbitals depend on the occupancy of the proton orbitals.
The $N=32,34$ shell gaps in $^{52}$Ca are thought to appear due to the 𝜈f$_{5/2}$ orbital sitting well above the 𝜈p$_{1/2}$ orbital to leave gaps on either side. One explanation for the disappearance of the $N=34$ magic number at larger $Z$ is that the when the 𝜋f$_{7/2}$ orbital starts filling, the tensor force coupling between the 𝜋f$_{7/2}$ protons and 𝜈f$_{5/2}$ neutrons reduces the energy of the 𝜈f$_{5/2}$ orbital. To experimentally probe this phenomenon we study titanium isotopes, two protons above calcium. We present results from in-beam gamma-ray spectroscopy of one-neutron knockout from $^{56,58}$Ti with the HiCARI gamma array and the BigRIPS and ZeroDegree spectrometers. Using the parallel momentum distribution of the outgoing ions, we can determine the angular momentum of the orbital from which the neutron is removed. Combined with the spectroscopic analysis, we aim to determine the relative position of the 𝜈f$_{5/2}$ with two protons in the 𝜋f$_{7/2}$ orbital, and identify whether it has already dropped below the 𝜈p$_{1/2}$ orbital.

Speaker: Martha Reece (GSI)

11:50 a.m. Investigations of the unbound states in 20C

The carbon isotopes, with $Z$=6 being the first spin-orbit shell gap originating from the splitting of the $1p_{1/2}$–$1p_{3/2}$ orbitals, provide an excellent ground to study changes in proton spin-orbit splitting from stability to the dripline. Neutron-rich carbon isotopes have been intensively investigated over the last decade. Transition probabilities, $B(E2;2^+\rightarrow0^+)$, have been measured up to $^{20}$C [1,2], revealing an increase from $^{16}$C to $^{20}$C. These $B(E2)$ values have been interpreted in terms of the mixing of unperturbed neutron and proton $2^+$ excitations, with the observed increase in collectivity explained by an enhanced contribution of proton excitations. This enhancement is likely due to a reduction of the proton $1p_{1/2}$–$1p_{3/2}$ spin-orbit splitting toward the dripline [3].

In a more recent experiment [4], neutron-rich carbon isotopes $^{16,18,20}$C were studied via proton removal reactions from nitrogen isotopes. Cross sections populating the ground and $2^+_1$ states were measured in each case. The results showed an increase in the proton component of the $2^+_1$ state, supporting a moderate reduction of the proton $1p_{1/2}$–$1p_{3/2}$ splitting towards the neutron dripline [4]. This study, as well as [3], further suggested that a mixed-symmetry $2^+$ state with an excitation energy around 7 MeV should be strongly populated in proton removal reactions from nitrogen isotopes. This state, lying above the neutron separation energy and therefore unbound, likely decays via neutron emission. Investigating this unbound $2^+$ state in carbon isotopes will provide critical experimental data to shed light on the evolution of the $Z$=6 spin-orbit splitting and benchmark theoretical models.

We present the investigation of the unbound states in $^{20}$C, populated via proton removal from $^{21}$N. The radioactive $^{21}$N beam was produced by the BigRIPS separator at RIBF and induced a proton removal reaction on a carbon target. The unbound states in $^{20}$C were analyzed using the SAMURAI spectrometer via invariant mass spectroscopy. In this report, the experimental setup, the data analysis as well as the preliminary results will be presented.

[1] M. Petri et al., Phys. Rev. Lett. 107, 102501 (2011).
[2] M. Petri et al., Phys. Rev. C 86, 044329 (2012).
[3] A.O. Macchiavelli et al., Phys. Rev. C 90, 067305 (2014).
[4] I. Syndikus et al., Phys. Lett. B 809, 135748 (2020).

Speaker: Sidong Chen (University of York)

12:10 p.m. Probing shell evolution in neutron-rich 50-54Ca: lifetime and Coulomb excitation measurements at RIBF

The structural evolution of neutron-rich Ca isotopes (Z = 20) has drawn significant experimental and theoretical interest, particularly concerning the emergence of sub-shell closures at N = 32 [1] and N = 34 [2]. While these closures are supported by excited-state energies [2], mass measurements [1, 3], and direct reaction cross sections [4, 5], the large charge radii observed in 50,52Ca [6] indicate potential (core breaking) proton excitations, challenging the magicity of 52Ca [7]. To elucidate the driving mechanism of the shell evolution in this exotic region, and to benchmark theoretical calculations towards the potentially doubly magic 60Ca, measurements of transition strengths are critical.

In this contribution, we report on two complementary experiments performed at the RIBF facility of the RIKEN Nishina Center, investigating electromagnetic transition strengths in 50-54Ca.

In the first experiment, we performed high-resolution gamma-ray spectroscopy to measure the lifetimes of excited states in 53Ca. The excited states were populated via multi-nucleon removal reactions of a Sc secondary beam on C and CH2 targets. Utilizing the HiCARI
(High-resolution Cluster Array at RIBF) array, excited state lifetimes are extracted through line-shape analysis, providing direct access to transition strengths.

Complementing this, a systematic study of E2 transition strengths in
50-54Ca was conducted using intermediate-energy Coulomb excitation. Neutron-rich Ca beams, produced via the fragmentation of a 345 MeV/nucleon 70Zn primary beam, were directed onto a 1-mm Au target. The BigRIPS-ZeroDegree beamline and DALI2+/HYPATIA array were utilized to measure the excitation cross sections, with nuclear excitation contributions disentangled using a 6-mm Be target.

The presentation will detail the experimental setups, the current status of both data analyses, and preliminary results. The measured transition strengths will be compared with state-of-the-art theoretical calculations to further discuss the complex shell structure along
the Ca isotopic chain beyond N = 28.

References:
[1] Wienholtz, F. et al. Nature 498, 346–349 (2013).
[2] Steppenbeck, D. et al. Nature 502, 207–210 (2013).
[3] Michimasa, S. et al. Phys. Rev. Lett. 121, 022506 (2018).
[4] Chen, S. et al. Phys. Rev. Lett. 123, 142501 (2019).
[5] Enciu, M. et al. Phys. Rev. Lett. 129, 262501 (2022).
[6] Garcia Ruiz, R. F. et al. Nature Phys. 12, 549–598 (2016).
[7] Gade, A. et al. Phys. Rev. C 74, 021302(R) (2006).

Speaker: Ting Gao (University of York)

12:30 p.m. → 2:00 p.m. Lunch

2:00 p.m. → 3:30 p.m. Thursday Afternoon Early Session: (Chair: Roelof Bijker)

2:00 p.m. Recent developments of ab initio calculations in light nuclei

The past decade has witnessed tremendous progress in theoretical and computational approaches to describing the atomic nucleus as a system of interacting protons and neutrons. In particular, ab initio calculations based on interactions and currents derived from chiral effective field theory have achieved an accurate description of key experimental quantities. In this talk, I will focus on selected electroweak observables in light nuclei and show that the level of accuracy now reached opens the possibility of using nuclear theory to address open questions in other areas of physics, such as neutrino physics.

Speaker: Prof. Sonia Bacca (Johannes Gutenberg University)

2:30 p.m. Approaching the N=20 Island of Inversion with the $^{29}$Mg(d,p)$^{30}$Mg reaction

We have studied the $^{29}$Mg(d,p)$^{30}$Mg reaction in inverse kinematics, with the first use of a reaccelerated rare-isotope beam from FRIB delivered to the SOLARIS solenoidal spectrometer. The N=20 Island of Inversion (IoI) at $^{32}$Mg is well known, arising from a diminished gap between the $sd$ and $fp$ neutron shells. Evidence for this modification comes from a variety of studies including mass measurements [1], neutron knockout [2], Coulomb excitation [3] and proton scattering [4]. A pioneering study of the two-neutron transfer reaction $^{30}$Mg(t,p)$^{32}$Mg [5] and theoretical analyses [6] of those data suggested that the $^{32}$Mg ground state is strongly deformed with significant contributions of 2p-2h and 4p-4h neutron excitations out of the $sd$ shell. Differing interpretations of the approach to N=20 in the Mg isotopes exist, however. Coulomb-excitation work from the MINIBALL experiment suggest that $^{30}$Mg is a spherical nucleus residing fully outside of the IoI [7], while other Coulex measurements [8] indicate that $^{30}$Mg is deformed, and knockout data [9] identify non-negligible $fp$-shell strength in $^{30}$Mg that is approximately 30% of that seen in $^{32}$Mg. The question of whether the transition to N=20 IoI is sudden, or occurs more gradually, with particle-hole excitations already playing a role in the structure of low-lying states in $^{30}$Mg, can also be addressed by studying neutron transfer to the low-lying 0$^+$ states in $^{30}$Mg with the $^{29}$Mg(d,p)$^{30}$Mg reaction. Furthermore, little information exists about the negative-parity states in $^{30}$Mg, which inform us about the $fp$-shell single-particle energies. Shell-model calculations yield different predictions about the energies of negative-parity excitations, and single-neutron transfer strongly populates such states. We studied the $^{29}$Mg(d,p)$^{30}$Mg reaction in inverse kinematics using a reaccelerated $^{29}$Mg beam produced by the ReA6 facility at FRIB. The $^{29}$Mg beam, with an intensity of approximately 40000 particles per second and energy of 8.46 AMeV, bombarded a 200 μg/cm$^2$ CD$_2$ target. Protons and recoiling $^{30}$Mg nuclei were detected with SOLARIS, providing high-resolution measurements for final states in $^{30}$Mg. The data suggest significant mixing between the ground and first-excited 0$^+$ states, clear evidence for several negative-parity excitations, and one new previously unobserved state. We will present these results, and discuss comparisons of the experimental observations with predictions from shell-model calculations.

This material is based upon work supported by the U. S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Numbers DE-SC0014552 (UCONN) and DE-AC02-6CH11357 (ANL) and used resources of the Facility for Rare Isotope Beams (FRIB) Operations, which is a DOE Office of Science User Facility under Award Number DE-SC0023633. SOLARIS is funded by the DOE Office of Science under the FRIB Cooperative Agreement DE-SC0000661.

[1] C. Thibault et al., Phys. Rev. C 12, 644 (1975).
[2] J.R. Terry et al., Phys. Rev. C 77, 014316 (2008).
[3] P. Doornenbal et al., Phys. Rev. Lett. 111, 212502 (2013), H.L. Crawford et al., Phys. Rev. C 93, 031303 (2016).
[4] S. Takeuchi et al., Phys. Rev. C 79, 054319 (2009).
[5] K. Wimmer et al., Phys. Rev. Lett. 105, 252501 (2010).
[6] A.O. Macchiavelli et al., Phys. Rev. C 94, 051303(R) (2016).
[7] O. Niedermaier et al., Phys. Rev. Lett. 94, 172501 (2005).
[8] V. Chisté et al., Phys. Lett. B 514, 233 (2001).
[9] J. R. Terry et al., Phys. Rev. C 77, 014316 (2008).

Speaker: Alan Wuosmaa (University of Connecticut)

2:50 p.m. Experimental Study of Electromagnetic Transitions in Neutron-rich ²²F

The evolution of nuclear shell structure at the interface between the p and sd shells remains a central problem in nuclear physics, where cross-shell excitations and proton–neutron correlations drive changes in nuclear structure. The odd–odd nucleus 22F lies just above the Z=8 shell closure and is particularly sensitive to excitations across the p–sd shell gap, making it an ideal system for probing this transition region.

Excited states in 22F were populated via the 9Be(18O, αp)22F fusion–evaporation reaction using a 55 MeV beam delivered by the ATLAS facility at Argonne National Laboratory. Prompt γ rays were detected with the GRETINA array in coincidence with recoils identified by the Fragment Mass Analyzer. Doppler-corrected γ-γ coincidence measurements enabled the construction of an expanded level scheme.

Several previously unobserved γ-ray transitions and new excited states were identified, significantly extending the known spectroscopy of 22F. Spin and parity assignments were constrained through angular distribution and linear polarization measurements, providing new insight into the structure of this odd–odd system.

The results are compared with ab initio calculations based on chiral effective field theory and place new constraints on the description of proton–neutron correlations and shell evolution at the p–sd boundary.

Speaker: Muzafar Ibrahim (University of Massachusetts Lowell)

3:10 p.m. Exploring Configurations in Neutron-Rich Si Isotopes

Understanding the evolution of nuclear shells with increasing nucleon number provides insight into how the fundamental interactions governing nuclear properties manifest at the scale of nuclear observables. One such region where this is particularly apparent is the $N=20$ island of inversion, where the nominally higher-lying $\nu(f_{7/2})$ shell falls below the $\nu(d_{3/2})$ and dominates the ground state configuration of $^{32}$Mg. Neutron rich Si isotopes lying at the northwestern boundary of the island of inversion have been of significant interest recently, as they represent a region where the evolution between the ''normal'' and ''intruder'' configurations are dominant. Specifically, the ground state of $^{32}$Si is predicted to have a pure $sd$-shell configuration with little-to-no $fp$-shell contributions to the low-energy states, while $^{34}$Si has been described as a ''transitional'' nucleus with dominant $sd$-shell ground state but significant $fp$-shell contributions in low-energy states. In this talk I will discuss the results of neutron-adding $^{31}$Si($d,p$)$^{32}$Si experiments recently performed using the HELIOS solenoidal spectrometer at ATLAS, as well as planned future experiments for the analogous $^{33}$Si($d,p$)$^{34}$Si reaction using SOLARIS at FRIB. The results and implications of these measurements will be addressed.

This work is supported in part by the U.S. Department of Energy Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 and with resources of ANL's ATLAS facility, a Department of Energy, Office of Science User Facility.

Speaker: Matthew Martin (Argonne National Laboratory)

3:30 p.m. → 4:00 p.m. Coffee Break

4:00 p.m. → 5:30 p.m. Thursday Afternoon Late Session: (Chair: Sonia Bacca)

4:00 p.m. Recent Results on Nuclear Structure from the University of Jyväskylä Accelerator Laboratory

The nuclear spectroscopy program at the Accelerator Laboratory of the University of Jyväskylä has for decades relied on combining a germanium-detector array with a recoil separator, enabling the use of the highly sensitive recoil-gating and recoil-decay tagging techniques. Since 2019, the JUROGAM 3 spectrometer has been operated together with the vacuum-mode MARA and gas-filled RITU separators in numerous experiments addressing a broad range of nuclear structure questions. The success of this experimental program is reflected in recent results on nuclei near the N=Z line, as well as in the heavier mass region. This presentation will discuss these recent results and outline ongoing and future nuclear structure studies of neutron-deficient nuclei in the A=30-50 mass region.

Speaker: Dr Panu Ruotsalainen (University of Jyväskylä)

4:30 p.m. Student Poster Award

Speaker: Guest Guest

4:50 p.m. Excited-State Lifetime Measurements in Neutron-Rich Ca, Ar Isotopes at INFN LNL

The isotopic mass region defined by the convergence of the Z = 20 and N = 28 magic numbers sits atop multiple areas of active study, offering a unique opportunity to constrain various distinct structural effects in a singular experiment. Working out towards the neutron-rich exotic Ca isotopes from the last stable isotope at $^{48}$Ca, closures of the $N$ = 32 and $N$ = 34 neutron sub-shells are expected to emerge based on the recent mass measurements [1] and high $2^+_1$ energies, while a monotonic increase in the nuclear radii from $^{48}$Ca to $^{52}$Ca suggests otherwise [2,3]. Looking proton deficient of this region, the evolution of $B(E2)$ values can be used to understand deformation and core breaking across the $N$ = 28 shell gap [4], approaching the 2nd island of inversion surrounding the collective $^{44}$Si [5]. Lifetime measurements of low-lying states in the yrast bands of $^{50,51,52}$Ca and $^{46,47,48}$Ar provides a mechanism of probing the largely unconstrained $B(E2)$ values for these states, providing a stringent test for the shell-model interactions in this region.

In 2024 at INFN LNL, a 305 MeV beam of $^{48}$Ca beam was delivered to a $^{238}$U target at the combined AGATA/PRISMA experimental station, populating $^{50,51,52}$Ca and $^{46,47,48}$Ar among other nearby isotopes in a multi-nucleon transfer reaction. Surrounding the $^{238}$U target, the high-purity germanium Advanced GAmma Tracking Array (AGATA) [6,7] was used to measure high-resolution $\gamma$-ray lineshapes from the states in the excited isotopes. These emitted recoil isotopes were then collected in the PRISMA large acceptance magnetic spectrometer [8], providing event-by-event resolution of the mass and atomic number. Two target configurations were used to study two distinct lifetime ranges using the Doppler-shift attenuation method (DSAM) and recoil distance Doppler-shift (RDDS) technique, utilizing a $^{238}$U target with a thick $^{93}$Nb backing and a $^{238}$U target separated from a $^{93}$Nb degrader in the Cologne Compact Plunger [9], respectively.

In this contribution, we will discuss the lifetime analysis of states in the Ca and Ar isotopes beyond $N$ = 28, using shell-model calculations to provide further context to these observations.

[1] S. Michimasa et al. (2018) Phys. Rev. Lett., 121, 022506
[2] G. Ruiz et al. (2016) Nature Physics, 12, 594
[3] M. Tanaka et al. (2020) Phys. Rev. Lett., 124, 102501
[4] A. Gade et al. (2003) Phys. Rev. C, 68, 014302
[5] M. Mougeot et al. (2020) Phys. Rev. C, 102, 014301
[6] S. Akkoyun et al. (2012) NIM A, 668, 26
[7] J.J. Valiente-Dobón et al. (2023) NIM A, 1049, 168040
[8] S. Szilner et al. (2007), Phys. Rev. C, 76, 024604
[9] M. Beckers et al. (2022) NIM A, 1042, 167418

Speaker: Beau Greaves (INFN-LNL)

5:10 p.m. Low-Energy Coulomb Excitation of Neutron Deficient 106,108Sn

A low-energy Coulomb excitation experiment which employed 106,108Sn radioactive ion beams was recently performed at the ReA6 facility of FRIB. The experiment utilized the SeGA-JANUS setup for coincident particle and gamma ray detection. The measurement, its motivation, and the experimental results will be presented. In particular, results on B(E2) transition strengths and previously-unknown Qs spectroscopic quadrupole moments will be shown. These results advance our understanding of shape and collectivity in an area of the nuclear chart very close to doubly-magic 100Sn.

This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC 52-07NA27344.

Speaker: Daniel Rhodes (Lawrence Livermore National Lab)

6:00 p.m. → 9:00 p.m. Conference Dinner

Fri, July 31

9:00 a.m. → 10:30 a.m. Friday Morning First Session: (Chair: Panu Ruotsalainen)

Friday morning first session

9:00 a.m. Results from Commissioning Nuclear Structure Experiments at RAON and the CENS Experimental Program

The RAON accelerator facility in Korea has recently commenced operations with its low-energy superconducting linear accelerator (SCL3) and ISOL system, providing new opportunities for nuclear structure studies with both stable and RI beams. The Center for Exotic Nuclear Studies (CENS) leads a broad experimental program at RAON, focusing on nuclear shell evolution, collective excitations, and the structure of exotic nuclei. To support these scientific goals, CENS has developed a large-scale gamma-ray detection system, ASGARD, consisting of up to 16 clover-type HPGe detectors, optimized for in-beam spectroscopy experiments. Several commissioning experiments employing ASGARD were conducted at the KoBRA spectrometer at RAON in Fall 2025. In this presentation, we will report on the early results from these commissioning experiments and provide an overview of ongoing and future nuclear structure programs lead by CENS.

Speaker: Prof. Kevin Insik Hahn (Center for Exotic Nuclear Studies, IBS)

9:30 a.m. Mass measurements of neutron-rich barium isotopes for the r-process and probing the evolution of nuclear structure

High-precision mass measurements of radioactive isotopes play a key role in advancing our understanding of nuclear structure and nuclear astrophysics. Nuclear masses provide direct access to binding energies and are essential inputs for testing nuclear models and studying shell evolution far from stability [1]. One area of interest is the rare-earth abundance peak around A = 165, which hints at a sub-shell closure or a change in nuclear structure [2].
The IGISOL (Ion Guide Isotope Separator On-Line) facility [3] in Jyväskylä provides a versatile approach to produce exotic nuclei. Reaction products from fusion, fission, or multi-nucleon transfer reactions are stopped in a gas cell, extracted, bunched and delivered to various experimental setups. The JYFLTRAP double Penning-trap mass spectrometer [4], located downstream of IGISOL, is dedicated to high-precision mass measurements. It combines a purification trap for isobaric cleaning with a precision trap where cyclotron frequencies are measured using time-of-flight ion-cyclotron-resonance [5] and phase-imaging techniques [6].
In this contribution, I present recent developments of the IGISOL facility and results of the JYFLTRAP setup at IGISOL, such as the mass measurement of neutron-rich barium isotopes with A = 146 - 151. Theoretical models predict strong structural changes including quadrupolar and octupolar deformation in this region [7]. The results of these measurements will be employed to investigate the effects of these deformations on the binding energies, benchmark nuclear models and constrain r-process simulations.

[1] M. Mumpower, et al., Prog. in Part. and Nucl. Phys. 86, 86–126 (2016).
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[3] I.D. Moore et al., Nucl. Inst. Meth. Phys. Res. B 317 (2013) 208.
[4] T. Eronen et al., European Physical Journal A 48, 46 (2012).
[5] König et al., Int. J. Mass Spectrom. Ion Process. 142, 95 (1995).
[6] D.A. Nesterenko et al., Eur. Phys. J. A 54, 154 (2018).
[7] Y. Cao et al., Phys. Rev. C 102, 024311 (2020).

Speaker: Simon Rausch (University of Jyväskylä)

9:50 a.m. Precision Mass Measurements of N≈Z Nuclei Near the Proton Dripline around A≈80

Understanding the mechanisms that cause nuclei in the ground or excited state to stabilize at certain shapes is pivotal to explaining structured evolution, especially far from closed shells. Rich systems for shape studies are found in the neutron-deficient A ≈ 80 region, around the N = Z nuclei $^{76}$Sr, $^{78}$Y, $^{80}$Zr, and $^{82}$Nb. Evidence from spectroscopic signatures indicates that the ground states of nuclei in this region are highly deformed. As such, there are opportunities to study deformation as well as contributions from the Wigner energy and pairing along the N = Z line. In this region, we used the Low Energy Beam and Ion Trap (LEBIT) Facility to measure the masses of $^{77,78,79}$Y, $^{79,80}$Zr and $^{82}$Nb to uncertainties <10 keV/c. This includes the first mass measurements of $^{77,78}$Y, $^{79}$Zr, and $^{82}$Nb as well as the first Penning trap measurements of $^{78m,79}$Y, which improve their precision by an order of magnitude. Additionally, the mass of $^{80}$Zr deviates from the previous LEBIT value [1], resulting in a major update to the surrounding region’s structure. These mass results and their implications will be presented.

[1] A. Hamaker, et al., Nat. Phys. 17, 1408–1412 (2021)

Speaker: Hannah Erington (The Facility for Rare Isotope Beams (Michigan State University))

10:10 a.m. Nuclear structure studies of neutron-rich lanthanides using precision mass spectrometry at TITAN, TRIUMF

Mass spectrometry plays an important role in different branches of physics including nuclear structure. Precise masses can help identify trends in nucleon separation energies, offering insight into shell closures and nuclear deformation. The TITAN (TRIUMF's Ion Trap for Atomic and Nuclear science) facility is dedicated to conducting high-precision and fast mass measurements by utilizing a state-of-the-art Multi-Reflection Time-of-flight Mass Spectrometer (MR-TOF-MS), and a Penning trap. In recent experimental campaigns, masses of several neutron-rich nuclides have been measured using the MR-TOF-MS, including that of many previously-unmeasured isotopes of lanthanides Eu, Tm and Yb. The measured masses were used to investigate nuclear structure effects in the rare-earth region, mainly in the hole-hole quadrant below the doubly magic $^{208}$Pb, such as subshell closures around $N \sim 104$, strong proton-neutron interaction in $^{186}$Hf and the potential onset of a prolate-to-oblate shape transition around $N \sim 116$, opening the door to investigating the effects of the strong force in a previously inaccessible region. These recent results along with an outlook of planned measurements in the region will be presented in this contribution.

Speaker: Dwaipayan Ray

10:30 a.m. → 11:00 a.m. Coffee Break

11:00 a.m. → 12:30 p.m. Friday Morning Second Session: (Chair: Sebastian Raeder)

11:00 a.m. New frontiers in collinear laser spectroscopy at COLLAPS: Shell structure in exotic Ca isotopes

Collinear laser spectroscopy provides high-precision access to nuclear spins, electromagnetic moments, and changes in mean-square charge radii of atomic nuclei. In this contribution, I will present an overview of recent progress at COLLAPS during CERN Run 3, with emphasis on spectroscopy of the neutron-rich calcium isotopes ${}^{53,54}\mathrm{Ca}$ and on major instrumental developments aimed at pushing the sensitivity frontier. Measurements on ${}^{53,54}\mathrm{Ca}$ address the debated emergence of a shell closure at N=32, reaching production yields down to a few ions per second. I will also discuss the new LIAF setup, which opens new opportunities for charge-radius measurements in light nuclei such as fluorine and oxygen through improved background suppression and novel detection concepts. Together, these developments establish the basis for future studies of very exotic species at radioactive facilities.

Speaker: Liss Vazquez Rodriguez (Max Planck Institute for Nuclear Physics)

11:30 a.m. Charge Radii and Magnetic Moments of Neutron-Rich Silicon Isotopes

This contribution will present the first laser spectroscopy measurements of neutron-rich silicon isotopes from stable 28Si up to 38Si, performed using the Resonance Ionization Spectroscopy Experiment (RISE) at the BEam COoling LAser spectroscopy (BECOLA) facility, located at the Facility for Rare Isotope Beams (FRIB). From the measured isotope shifts and hyperfine structure, we extracted the nuclear magnetic dipole moments of odd-N silicon isotopes and differential mean-square nuclear charge radii of 28-36,38Si.
The silicon isotopic chain, having a proton sub-shell closure at Z=14, serves as an important probe of nuclear structure [1,2], especially in the vicinity of the suggested doubly magic 34Si at N=20, for which recent studies suggest the presence of a central depletion or bubble-like structure in 34Si [3-7]. These results provide a comprehensive study of the evolution of nuclear shell structure and collectivity across N=20, offering an important guide for the development of nuclear theory.

[1] Yang, X. et al., PPNP 129, 104005 (2023)
[2] König, K. et al., Phys. Rev. Lett. 132, 162502 (2024)
[3] Mutschler et al., Nature Phys. 13, 152 (2017)
[4] Sorlin et al., Phys. Lett. B 809, 135740 (2020)
[5] Duguet, T. et al., Phys. Rev. C 95, 034319 (2017)
[6] Zhang, S. et al., arXiv:2411.17462 (2025)
[7] Kay et al., Phys. Rev. Lett.119, 182502 (2017)

This work is supported in part by NSF grant No. PHY-21-11185 and DOE Office of Science Award No. DE-SC0000661.

Speaker: Fabian Camilo Pastrana Cruz (Massachusetts Institute of Technology)

11:50 a.m. Laser-radio-frequency double-resonance spectroscopy of 209Bi for the extraction of its nuclear magnetic octupole moment

Nuclear electromagnetic moments provide sensitive probes of the distribution of charge and magnetization inside the nucleus, yet higher-order moments remain largely unexplored. Current high-resolution laser spectroscopy techniques allow to achieve precisions of the order of 1 MHz [1], giving access to magnetic dipole and electric quadrupole moments. However, as the multipole order increases, the magnitude of the shift in the atomic energy levels decreases rapidly, from ~ GHz for the dipole to hundreds of MHz for the quadrupole and only hundreds of kHz for the octupole, with even smaller shifts expected for higher orders, leaving the octupole and beyond out of reach of standard spectroscopic techniques. The magnetic octupole moment is nevertheless of particular interest, as it offers a rare window on subtle aspects of the nuclear magnetization distribution and thus provides a stringent test for nuclear-structure models.

In this work, we target the magnetic octupole moment of stable $^{209}$Bi through a precision measurement of the hyperfine structure of its atomic ground state $^4S_{3/2}$. With one valence proton outside the doubly magic $^{208}$Pb core, $^{209}$Bi is a benchmark near-single-particle system in which experimental results can be confronted directly with modern nuclear-structure calculations.

To enable this measurement, we have developed at KU Leuven an atomic beam apparatus for laser-radio-frequency double-resonance spectroscopy [2]. Beyond the specific case of $^{209}$Bi, this effort is motivated by the longer-term goal of extending the method to radioactive isotopes, where precision measurements of higher-order moments could provide new structural information far from stability. The setup and analysis procedure were first developed and validated using potassium, allowing the dominant sources of systematic uncertainty to be identified and controlled before moving to bismuth.

We will present the performance of the apparatus, results from the potassium commissioning measurements, and highest-precision hyperfine-structure data to date on $^{209}$Bi. Combined with state-of-the-art atomic structure calculations, these measurements will enable the extraction of a precise magnetic octupole moment for $^{209}$Bi and provide a new benchmark for the description of magnetization properties in heavy nuclei.

[1] P. Campbell, I.D. Moore, and M.R. Pearson, ’Laser spectroscopy for nuclear structure physics’, Progress in Particle and Nuclear Physics, vol. 86, pp. 127-180, 2016.
[2] W.J. Childs, ’Overview of laser-radiofrequency double-resonance studies of atomic, molecular, and ionic beams’, Physics Reports, vol. 211.3, pp. 113-165, 1992.

Speaker: Anita Candiello (Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium)

12:10 p.m. Collinear Laser Spectroscopy far from stability: Mg and Cd

In recent years, significant progress in nuclear structure theory has been driven by the availability of precise experimental data on short-lived nuclei with neutron-to-proton ratios far from those at the valley of stability in the nuclear chart. Collinear Laser Spectroscopy (CLS) is a powerful technique for obtaining nuclear ground-state properties such as spins, electromagnetic moments, and charge radii.

To access exotic radionuclides with very low production yields, the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS) was conceived to enhance the sensitivity of fluorescence-based CLS. It is based on a unique high-energy (>10 keV) multi-reflection time-of-flight (MR-ToF) device, which utilizes two electrostatic mirrors to reflect ions back and forth for several thousands of revolutions. Hence, at MIRACLS, ion bunches are probed by the spectroscopy laser many times per measurement cycle to obtain higher measurement statistics compared to conventional, single-passage CLS. The resulting improvement in sensitivity allows the probing of isotopes with yields as low as 5 ions per second. In this way, radionuclides that would have been impossible to probe with conventional CLS techniques due to their low production yield and short half-lives now become accessible with the MIRACLS approach.

With MIRACLS, previous measurements have recently been extended to uncharted magnesium ($^{33, 34}$Mg) and cadmium ($^{98,99}$Cd) isotopes. The determination of charge radii of neutron-rich Mg isotopes allows us to probe the structure of nuclei in the $N=20$ island of inversion, an area of the nuclear chart where conventional shell closures disappear. Previously measured magnesium isotopes show a steady increase in charge radii up to $^{32}$Mg [1], with no indication of the shell closure, and our latest results on $^{33, 34}$Mg will provide valuable insight into the trend beyond $N=20$, acting as a stringent benchmark for new ab initio calculations motivated by our measurements.

In this oral contribution, the MIRACLS technique will be introduced and results from recent laser spectroscopy experiments on the aforementioned magnesium and cadmium isotopes will be presented.

References
[1] D. T. Yordanov et al., PRL, 108:042504 (2012)

Speaker: Anthony Roitman (McGill University)

12:30 p.m. → 12:45 p.m. Closing: Chair: Corina Andreoiu