Prolate-Spherical Shape Coexistence at N=28 in $^{44}$S

TL;DR

This paper investigates shape coexistence in $^{44}$S using spectroscopy, measuring decay rates and transition probabilities, and finds evidence for prolate-spherical shape coexistence with weak mixing between configurations.

Contribution

It provides the first measurements of decay rates for the 0$^+_2$ isomer in $^{44}$S and demonstrates shape coexistence through shell model comparisons and a two-level mixing model.

Findings

Measured decay rates and transition probabilities for $^{44}$S.

Evidence for prolate-spherical shape coexistence.

Weak mixing between different nuclear shapes.

Abstract

The structure of $^{44}$S has been studied using delayed $\gamma$ and electron spectroscopy at \textsc{ganil}. The decay rates of the 0$^+_2$ isomeric state to the 2$^+_1$ and 0$^+_1$ states have been measured for the first time, leading to a reduced transition probability B(E2~:~2$^{+}_1$$\rightarrow$0$^{+}_2)$= 8.4(26)~e$^2$fm$^4$ and a monopole strength $\rho^2$(E0~:~0$^{+}_2$$\rightarrow$0$^{+}_1)$ =~8.7(7)$\times$10$^{-3}$. Comparisons to shell model calculations point towards prolate-spherical shape coexistence and a phenomenological two level mixing model is used to extract a weak mixing between the two configurations.