High-spin structures of five N=82 isotones: 136Xe, 137Cs, 138Ba, 139La, and 140Ce

TL;DR

This study explores high-spin states in five N=82 isotones, revealing new structures, identifying an isomeric state in 139La, and confirming proton and neutron excitations through experimental data and shell-model calculations.

Contribution

First identification of high-spin states in 139La and extension of known structures in four other N=82 isotones, with detailed analysis and shell-model confirmation.

Findings

First high-spin states of 139La identified

Isomeric state with 315 ns half-life found in 139La

High-spin states in other isotones extended and confirmed by shell-model

Abstract

Five N=82 isotones have been produced in two fusion-fission reactions and their gamma-rays studied with the Euroball array. The high-spin states of 139La have been identified for the first time, while the high-spin yrast and near-to-yrast structures of the four others have been greatly extended. From angular correlation analysis,spin values have been assigned to some states of 136Xe and 137Cs. Several cascades involving gamma-rays of 139La have been found to be delayed, they deexcite an isomeric state with T1/2= 315(35) ns located at 1800-keV excitation energy. The excited states of these five N=82 isotones are expected to be due to various proton excitations involving the three high-j subshells located above the Z=50 shell closure. This is confirmed by the results of shell-model calculations performed in this work. In addition, high-spin states corresponding to the excitation of the neutron core have been unambiguously identified in 136Xe, 137Cs, and 138Ba.