Shape Coexistence and Mixing of Low-Lying $0^+$ States in $^{96}$Sr

TL;DR

This study investigates shape coexistence and mixing in low-lying $0^+$ states of $^{96}$Sr using transfer reactions and gamma decay analysis, revealing strong shape mixing and multiple configurations.

Contribution

It provides the first experimental determination of neutron $[2s_{1/2}]^2$ content in $^{96}$Sr's $0^+$ states and compares these with shell model predictions, highlighting shape coexistence.

Findings

Spectroscopic factors for $^{96}$Sr states were measured.

Strong shape mixing with mixing strength $a^2=0.40(14)$ was observed.

Results indicate coexistence of three configurations in $^{96}$Sr.

Abstract

The low energy excited $0_{2,3}^+$ states in $^{96}$Sr are amongst the most prominent examples of shape coexistence across the nuclear landscape. In this work, the neutron $[2s_{1/2}]^2$ content of the $0_{1,2,3}^+$ states in $^{96}$Sr was determined by means of the d($^{95}$Sr,p) transfer reaction at the TRIUMF-ISAC2 facility using the SHARC and TIGRESS arrays. Spectroscopic factors of 0.19(3) and 0.22(3) were extracted for the $^{96}$Sr ground and 1229~keV $0^+$ states, respectively, by fitting the experimental angular distributions to DWBA reaction model calculations. A detailed analysis of the $\gamma$-decay of the isomeric $0_3^+$ state was used to determine a spectroscopic factor of 0.33(13). The experimental results are compared to shell model calculations, which predict negligible spectroscopic strength for the excited $0^+$ states in $^{96}$Sr. The strengths of the excited $0_{2,3}^+$ states were also analyzed within a two-level mixing model and are consistent with a mixing strength of $a^2$=0.40(14) and a difference in intrinsic deformations of $|\Delta \beta|=0.31(3)$. These results suggest coexistence of three different configurations in $^{96}$Sr and strong shape mixing of the two excited $0^+$ states.