Speaker
Description
Mass spectrometry is invaluable for probing the essential characteristics of nuclei, particularly their binding energy. The FRS Ion Catcher at GSI employs a Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) to achieve precise, fast, and sensitive mass measurements, crucial for studying exotic nuclei far from stability. Previous investigations, have scrutinized properties of nuclei surrounding the heaviest N=Z double-magic nucleus, $^{100}$Sn [Horn], revealing discrepancies in properties like $Q_{ec}$ and production cross-sections [Hinke, Lubos].
The stability of nuclei along the N=Z line persists up to $^{40}$Ca (N=Z=20), beyond which, instability prevails. This increasing divergence from stability poses challenges for both production and measurement techniques in reaching the heaviest N=Z nuclei. In a recent study it was possible to determine the mass value of $^{100}$In, based on this and trends in the shifted two-neutron separation energy, the older $Q_{ec}$ value for $^{100}$Sn is favoured [Moug]. In the study that will be presented, mass measurements of isotones along the N=50 line (44$\leq$Z$\leq$48) approaching $^{100}$Sn were conducted, yielding measurements for 14 ground and two isomeric states [Moll].
The excitation energy of the long-lived isomer in $^{94}$Rh was determined for the first time and together with shell model calculations allowed a spin-parity assignment of the observed states.
First direct mass measurement of $^{98}$Cd provided a much more accurate and trustful $Q_{ec}$ value than previous mass measurement methods. Systematic investigations of the shifted two-neutron shell-gap, utilizing the newly acquired masses were performed, confirming the results of the previous study, favouring specific $Q_{ec}$ values [Hinke]. Moreover, the $Q_{ec}$ value obtained for $^{98}$Cd was also employed to analyze the Gamow-Teller (GT) strength trend along the N=50 isotones, which also has been compared to new state-of-the art calculations utilizing a large-scale shell model (LSSM). This results strongly support the newer $Q_{ec}$ values measured for $^{100}$Sn [Lubos].
[Moll] A. Mollaebrahimi et al., Phys. Lett. B 839 (2023) 137833
[Moug] Mougeot et al., Nat. Phys. 17, 1099–1103 (2021).
[Horn] C. Hornung et al., Phys. Lett. B 802 (2020) 135200
[Hinke] C.B. Hinke, et al., Nature 486 (2012) 341.
[Lubos] D. Lubos, et al., Phys. Rev. Lett. 122 (2019) 222502.
