Low spin spectroscopy of neutron-rich Cl 43 , 44 , 45 via β - and β n decay
In this article, β - decay studies of neutron-rich isotopes 43,45 S performed at the National Superconducting Cyclotron Laboratory are reported. β -delayed $\gamma$ transitions were detected by an array of 16 clover detectors surrounding the Beta Counting Station, which consists of a 40×40 double-sided silicon strip detector followed by a single-sided silicon strip detector. β -decay half-lives were extracted for 43,45 S by correlating implants and decays in the pixelated implant detector and by considering further coincidences with $\gamma$ transitions in the daughter nuclei. Further, the level structures of 43,45 Cl are expanded by the addition of 20 and 8 new $\gamma$ transitions in 43 Cl and 45 Cl respectively, and core-excited negative-parity states were observed in both nuclei for the first time. For 45 S, a large fraction of the β -decay strength was observed feeding neutron-unbound states in 45 Cl, which, decaying by delayed neutrons, populated excited states in the β 1 n daughter, 44 Cl. Experimental observations were compared to detailed shell-model calculations using the SDPFSDG-MU interaction to highlight the role of the diminished N = 28 neutron shell gap and the near degeneracy of the proton s 1/2 and d 3/2 orbitals in the structure of the neutron-rich Cl isotopes. The current work also provides further support to a ground-state spin-parity assignment of 3/2 + in 45 Cl.