Investigation into behavior of weakly-bound proton via B(GT) measurement for the beta decay of Si-24

The beta-decay spectroscopy on Si-24 was carried out in order to investigate the behavior of a weakly-bound s-wave proton. We observed two beta transitions to low-lying bound states in Al-24 for the first time. The Gamow-Teller transition strengths B(GT) to the 1(1)(+) and 1(2)(+) states were deduced to be 0.13(2) and 0.14(1), which were smaller than that of mirror nucleus Ne-24 by 22 % and 10 %, respectively. These mirror asymmetries of B(GT) indicate the configuration change in the wave function. By comparing with theoretical shell-model calculations, it is implied that the configuration change is attributed to the lowering of the 1s(1/2) orbital.