Speaker
Description
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