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

β- decay of Tz=+11/2 nuclei 37Al and 39Si was studied to obtain information about excited states in the daughter and granddaughter nuclei. New information on excited states has been obtained for 37,39P, whereas level schemes for 37Si and 37,39S 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 β- 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 β- decay of very neutron-rich nuclei also illustrates how the Gamow-Teller (GT) strength distribution changes with neutron excess. Comparing β- decay of 37,39Si presented here with 1Si 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. [ABSTRACT FROM AUTHOR]