Isomerism and persistence of theN=82shell closure in the neutron-richSn132region

Abstract

The occurrence of seniority isomers in semimagic nuclei is a clear indication for shell closure. By performing large-scale shell-model calculations in a model space that allows excitations across the $N=82$ neutron and $Z=50$ proton shell gaps, we investigate the isomerism along the $N=82$ isotonic chain. The calculation describes well the properties of the experimentally observed ${8}^{+}$ isomeric state and the other low-lying states in $^{126}\mathrm{Pd},^{128}\mathrm{Pd}$, and $^{130}\mathrm{Cd}$. We further predict energy levels and $E2$ transitions for $^{126}\mathrm{Ru}$ and $^{124}\mathrm{Mo}$ as their structure information is necessary for a complete understanding of the seniority picture. Our results, together with other existing evidence, support the conclusion that the shell closure persists at the neutron number $N=82$ in the neutron-rich region.