Different seniority states of $^{119-126}$Sn isotopes: shell-model description

Abstract

Abstract In the present work, available experimental data up to high-spin states of $^{119-126}$Sn isotopes with different seniority ($v$), including $v = 4$, 5, 6, and 7, are interpreted with the shell model, by performing shell-model calculations in the 50–82 valence shell composed of $1g_{7/2}$, $2d_{5/2}$, $1h_{11/2}$, $3s_{1/2}$, and $2d_{3/2}$ orbitals. The results are compared with the available experimental data. These states are described in terms of broken neutron pairs occupying the $h_{11/2}$ orbital. Possible configurations of seniority isomers in these nuclei are discussed. The breaking of three neutron pairs is responsible for generating high-spin states. The isomeric states $5^-$, $7^-$, $10^+$, and $15^-$ of even Sn isotopes, and isomeric states $19/2^+$, $23/2^+$, $27/2^-$, and $35/2^+$ of odd Sn isotopes, are described in terms of different seniority. For even Sn isotopes, the isomeric states $5^-$, $7^-$, and $10^+$ are due to seniority $v = 2$; the isomeric state $15^-$ is due to seniority $v = 4$, and, in the case of odd Sn isotopes, the isomeric states $19/2^+$, $23/2^+$, and $27/2^-$ are due to seniority $v = 3$, and the isomeric state $35/2^+$ in $^{123}$Sn is due to seniority $v = 5$. These are maximally aligned spins, which involve successive pair breakings in the $\nu (h_{11/2})$ orbital.