Shell-model study of weak β-decays relevant to astrophysical processes

Shell-model studies on the weak β -decay in nuclei relevant to astrophysical processes are carried out. The β -decay rates, as well as electron-capture rates in the sd - pf shell induced by Gamow–Teller (GT) transition, are evaluated in astrophysical environments. The weak rates for the Urca pair of nuclei with A = 31 in the island of inversion, which are important for the nuclear Urca processes in neutron star crusts, are investigated by shell-model calculations in the sd – pf shell. The GT strength is evaluated in the sd – pf shell for selected β -decays in the sd -shell nuclei, and the effects of the expansion of the configuration space on the quenching of the axial–vector coupling are examined. β -decay rates induced by first-forbidden (FF) transitions are studied by the Behrens–Bühring (BB) method for the isotones with N = 126 and compared with the Walecka method. The important role of the electron distortions in the β -decays of 206 Hg and 207 Tl is pointed out.