Hindered proton collectivity in the proton-rich nucleus ²⁸S: Possible magic number at Z = 16

The reduced transition probability B(E2; 0+g s 2+1 ) for the protonrich nucleus 28S was determined experimentally using Coulomb excitation at 53 MeV/nucleon. The resultant B(E2) value is smaller than those of neighboring N = 12 isotones and Z = 16 isotopes. The ratio of neutron/ proton transition matrix amplitudes for the 0+ gs 2+1 transition were obtained to be 1:9(2) N=Z from the present result and known B(E2) value in the mirror nucleus 28Mg. These results indicate the emergence of the magic number Z = 16 in 28S.