Hindered Proton Collectivity in the Proton-rich Nucleus ~(28)S: Possible Magic Number Z = 16

摘要

The reduced transition probability B(E2;0_(gs)~+ → 2_1~+) for the proton-rich nucleus ~(28)S was determined experimentally using intermediate-energy Coulomb excitation. The resultant B(E2) value 181(31) e~2fm~4 is smaller than those of neighboring N = 12 isotones and Z = 16 isotopes. The double ratio |M_n/M_p|/(N/Z) of the 0_(gs)~+ → 2_1~+ transition in ~(28)S was obtained to be 1.9(2) by evaluating the M_n value from the known B(E2) value of the mirror nucleus ~(28)Mg, showing the hindrance of proton collectivity relative to that of neutrons. These results indicate the emergence of the magic number Z = 16 in ~(28)S.