β − decay of T z = + 11 2 isotopes Al 37 and Si 39 : Understanding Gamow-Teller strength distribution in neutron-rich nuclei

beta(-) decay of T-z = +11/2 nuclei Al-37 and Si-39 was studied to obtain information about excited states in the daughter and granddaughter nuclei. New information on excited states has been obtained for P-37,P-39, whereas level schemes for Si-37 and S-37,S-39 were confirmed and expanded on as compared to the most recent investigations. For the nuclei studied, the valence proton and neutron occupy different major shells with opposite parities, hence, the beta(-) decay preferentially and primarily populates core-excited 1p1h intruder states with a parity opposite to the ground state of the daughter nucleus. These low-lying intruder states shed light on the N = 20 shell gap and its evolution with neutron number. The beta(-) decay of very neutron-rich nuclei also illustrates how the Gamow-Teller (GT) strength distribution changes with neutron excess. Comparing beta(-) decay of Si-37,Si-39 presented here with Si-38,Si-40 from a previous study, we clearly see an even-odd effect in the GT strength distribution with the decay from even-even nuclei showing strong low-lying strength whereas for the odd A being very fragmented. Configuration interaction shell-model calculations with the state-of-art SDPFSDG-MU effective interaction were performed to understand the structure of the 1p1h states and explore the GT strength distribution.