Identification of a β-decaying isomer in ³⁶Al and studying the structure of neutron-rich Mg and Al isotopes in the first FRIB experiment.

A long-lived isomeric state in ³⁶Al was identified for the first time via β-decay of ³⁶Mg and ³⁶Al. Neutron-rich ³⁶Mg and ³⁶Al were produced at the Facility for Rare Isotope Beams(FRIB) via projectile fragmentation of a ⁴⁸Ca beam of energy 172.3 MeV/u. The beam was impinged on a 8.89 mm thick ⁹Be target. The fragmented beam was delivered to the β-decay station after being resolved by the Advanced Rare Isotope Separator(ARIS). A fast timing scintillator of 2mm thickness followed by two Si PIN detectors, each 500 μm thick, were placed in the upstream side for the particle identification (PID). The energies lost by the ions in PIN2 were plotted against the time-of-flight between the ARIS scintillator and the sintillator at the decay station in order to generate the PID. At the center of the decay station, a 5mm thick YSO scitillator implantation detector was placed. The β-delayed γ-rays were identified with 11 clover and 15 LaBr₃ detectors. The determination of the half-lives of the parent nuclei was facilitated by integrating complementary data from a similar β-decay experiment carried out at the National Superconducting Cyclotron Laboratory (NSCL). The β-delayed γ-ray transitions were reported in ³⁶Al and ³⁶Si for the first time and their level schemes were built from the correlated β-decays of ³⁶Mg and ³⁶Al. The β-decay of ³⁶Mg provided insights into previously unknown excited energy states of ³⁶Al, as prior to this investigation, only ground state information was available. A long-lived isomeric state in ³⁶Al was identified, undergoing β-decay to an excited state of ³⁶Si. The experimental findings were interpreted using nuclear configuration interaction studies employing the FSU shell-model Hamiltonian. These results contribute significantly to our understanding of the structural characteristics of more exotic, neutron-rich nuclei, a domain that will be further explored with the cutting-edge capabilities of new-generation facilities such as FRIB.