Complete decay spectroscopy of neutron-rich chlorine isotopes

by Dr Ian Cox (UTK)

Monday 25 Aug 2025, 13:50 → 14:50 US/Eastern

604 (Nielsen)

Properties of nuclei far from stability can differ significantly from their stable counterparts, yet in these exotic nuclei, interactions between nucleons can be precisely studied.  The development of fragmentation facilities, such as the Facility for Rare Isotope Beams (FRIB), has greatly expanded the range of nuclei available for study and led to advancements in measurement techniques.  In the region south of ⁴⁸Ca, Gamow-Teller transitions transform sd and pf neutrons into their respective spin-orbit partner orbitals.  By pushing to more neutron-rich nuclei, residual daughter states can occur both above and below the neutron separation energy.  This necessitates complete decay spectroscopy across the entire beta-decay energy window.  The FRIB Decay Station Initiator (FDSi) recently successfully measured the complete decay spectroscopy of ⁴⁵Cl using a two-focal plane approach [I. Cox, et al. Phys. Rev. Lett. 132, 152503 (2024)].  This measurement probed highly excited states in ⁴⁵Ar, created by proton excitation into the pf shell and rigorously tested state-of-the-art shell model predictions. Extended decay strength measurement of chlorine isotopes with N=27-30 allow for an expansive test of theoretical predictions across the N=28 shell gap, while transitioning from spherical to deformed nuclei.  The results will be discussed in comparison to large-scale shell model calculations using the SDPF-MU interaction to benchmark the Z=20 shell gap in the region.