Shape evolution in heavy sulfur isotopes and erosion of the $N=28\mathrm{}$ shell closure

The structure of neutron-rich ${}^{40,42,44}\mathrm{S}$ nuclei has been investigated through in-beam $\gamma$-ray spectroscopy using the fragmentation reaction of a 60 MeV A ${}^{48}\mathrm{Ca}$ beam on a thin Be target. $E_{\gamma },$ $I_{\gamma },$ $\gamma \gamma$-coincidence, and $\gamma$-ray angular distributions were measured for each produced fragment. The level schemes previously containing only a single $\gamma$ transition were extended, and spin values were proposed for the new states. The experimental results were interpreted by use of microscopic collective-model and large-scale shell-model calculations. The results of the model calculations are consistent with each other, and give a reasonable description of the experimental results. Both models predict an erosion of the $N=28\mathrm{}$ shell closure at $Z=16\mathrm{}$ and suggest a deformed ground state for ${}^{40,42}\mathrm{S}$ and a spherical-deformed mixed configuration for ${}^{44}\mathrm{S}.$