High-spin structures of ${}_{54}^{136}$Xe, ${}_{55}^{137}$Cs, ${}_{56}^{138}$Ba, ${}_{57}^{139}$La, and ${}_{58}^{140}$Ce : A shell model description

Abstract

In the present work recently available experimental data [A. Astier et al, Phys. Rev. C 85, 064316 (2012)] for high-spin states of five N=82 isotones, ${}_{54}^{136}$Xe, ${}_{55}^{137}$Cs, ${}_{56}^{138}$Ba, ${}_{57}^{139}$La, and ${}_{58}^{140}$Ce have been interpreted with state-of-the-art shell model calculations. The calculations have been performed 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. We have compared our results with the available experimental data for excitation energies including high-spin states, occupancy numbers and transition probabilities. As expected the structure of these isotones are due to proton excitations across Z=50 shell. The structure of the positive-parity states are mainly from $(\pi g_{7/2}\pi d_{5/2}{)}^n$ and $(\pi g_{7/2}\pi d_{5/2}{)}^{n-2}(\pi h_{11/2}{)}^2$ configurations, while the negative-parity states have $(\pi g_{7/2}\pi d_{5/2}{)}^n(\pi h_{11/2}{)}^1$ configuration. Additionally, for the ${}_{54}^{136}$Xe, ${}_{55}^{137}$Cs and ${}_{56}^{138}$Ba isotones the excitation of the neutrons across N=82 gap is important.

Comments: 14 pages, 6 figures