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

TL;DR

This study uses advanced shell model calculations to interpret high-spin states in five N=82 isotones, matching experimental data and revealing proton and neutron excitation configurations across shell gaps.

Contribution

The paper provides a detailed shell model analysis of high-spin states in five N=82 isotones, including comparisons with experimental data and insights into proton and neutron configurations.

Findings

Shell model reproduces excitation energies and transition probabilities.

Positive-parity states mainly from proton configurations involving g7/2, d5/2, h11/2 orbitals.

Neutron excitations across N=82 are significant in some isotones.

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, $^{136}_{54}$Xe, $^{137}_{55}$Cs, $^{138}_{56}$Ba, $^{139}_{57}$La, and $^{140}_{58}$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 $^{136}_{54}$Xe, $^{137}_{55}$Cs and $^{138}_{56}$Ba isotones the excitation of the neutrons across N=82 gap is important.