Shape evolution in heavy sulfur isotopes and erosion of the N=28 shell closure -: art. no. 054302

The structure of neutron-rich S-40,S-42,S-44 nuclei has been investigated through in-beam gamma-ray spectroscopy using the fragmentation reaction of a 60 MeV A Ca-48 beam on a thin Be target. E-gamma, I-gamma, gammagamma-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 shell closure at Z=16 and suggest a deformed ground state for S-40,S-42 and a spherical-deformed mixed configuration for S-44.