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

Abstract

The structure of ${}^{44}$S has been studied using delayed ${\hat{I}}^3$ 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^{+}$$\to$0${}_2^{+})$= 8.4(26)~e${}^2$fm${}^4$ and a monopole strength $\ddot{I}{}^2$(E0~:~0${}_2^{+}$$\to$0${}_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.

5 pages, 3 figures, accepted for publication in Physical Review Letters