Beta-delayed proton decays ofP27andCl31: Gamow-Teller decays with largeQvalues

The beta-delayed proton emissions of the odd-Z, $T_z$=-(3/2) nuclei ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$ and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$ have been studied. This work represents the first observation of the decay of ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$, yielding a half-life of 260±80 ms, and completes the series of beta-delayed proton emitters with $T_z$=-(3/2) in the sd shell. Several new proton groups were attributed to the decay of ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$; their half-lives are consistent with a previous observation. The estimated logft values of the observed transitions for both ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$ and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$ are consistent with clustering of the beta strength above the isobaric analog states in the daughter nuclei as predicted by a complete (1s,0d)-space shell-model calculation. The observed half-lives are in good agreement with the shell-model predictions which include a quenching of the Gamow-Teller strength by a factor of 0.6, in accordance with earlier observations.