Speaker
Description
Heavy $N=Z$ nuclei and nuclei in their vicinity are highly interesting to study; they can provide important insights about nuclear structure, symmetries and interactions and have a high impact in modelling nuclear astrophysics processes ($rp$-process, $\nu p$-process). A few examples of the striking phenomena emerging in these nuclei are the formation of high-spin isomeric states, the direct and/or $\beta$-delayed proton emission from ground or excited states and the strong resonances in Gamow-Teller transitions close to the proton dripline.
Precision experiments with thermalized projectile and fission fragments will be possible at the Super-FRS Ion Catcher at FAIR in Early Science/First Science stationed in front of the High-Energy Branch using a gas-filled cryogenic stopping cell (CSC) and a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). Envisioned first experiments include measurements of branching ratios (e.g., $\beta$-delayed (multi)neutron emission probabilities), masses and lifetimes as well as the in-cell production of exotic nuclei by multi-nucleon transfer reactions with secondary beams. In this contribution, work towards these goals will be presented together with results of proof-of-principle experiments, including highly accurate direct mass measurements of exotic nuclei $(\delta m/m \sim 10^{-8})$ that are already possible at the FRS Ion Catcher (FRS-IC), which consists of the existing prototype CSC together with the MR-TOF-MS.
Recent results at the FRS-IC, achieved within FAIR Phase-0, include the first direct mass measurement of $^{98}$Cd, which allowed to study the evolution of Gamow-Teller transition strengths (B(GT)) for even-even $N=50$ and $N=52$ isotones [1]. Comparing experimental and theoretical B(GT) values sheds more light on the controversy around the $Q_\textrm{EC}$ value of $^{100}$Sn [2,3,4]. The mass of $^{93}$Pd was measured directly for the first time, reducing the mass uncertainty by an order of magnitude. The result shows that the excitation energies of the presumed parent states of the one-proton (1p) and two-proton (2p) decay in $^{94}$Ag differ from each other by 10 standard deviations, which represents an important step towards further unraveling the riddles surrounding these decay branches, the investigations of which were summarized in Refs. [5,6]. Among the scenarios, which could resolve this apparent contradiction, the possibility of the existence of two structurally different, high-spin states in $^{94}$Ag, feeding the 1p and 2p decay branches was studied performing state-of-the-art shell-model and mean-field calculations.
[1] A. Mollaebrahimi et al., Phys. Lett. B 839, 137833 (2023).
[2] C. B. Hinke et al., Nature 486 (2012) 341.
[3] D. Lubos et al., Phys. Rev. Lett. 122 (2019) 222502.
[4] M. Mougeot et al., Nat. Phys. 17, 1099-1103 (2021).
[5] A. Kankainen et al., Eur. Phys. J. A 48, 49 (2012).
[6] E. Roeckl and I. Mukha, Int. J. Mass. Spectrom. 349-350, 47 (2013).
| Email address | gkripko@ed.ac.uk |
|---|---|
| Classification | Ion guide, gas catcher, and beam manipulation techniques |
