Seniority isomerism in proton-rich N=82 isotones and its indication to stiffness of the Z=64 core - art. no. 054304

The 10(+) and 27/2(-) isomers of the Z>64, N=82 nuclei are investigated in the shell-model framework. We derive an extended seniority reduction formul a for the relevant E2 transition strengths. Based on the extended formula, as well as on the approximate degeneracy among the Oh(11/2), 2s(1/2), and 1 d(3/2) orbits, we argue that the B(E2) data require the Gd-146 core excitat ion. The energy levels of both parities and the B(E2) values are simultaneo usly reproduced by a multi-j shell-model calculation with the modified surf ace-delta interaction,if the excitations from (0g(7/2)1 d(5/2)) to (Oh(11/2 )2S(1/2)1d(3/2)) are taken into account.