Collectivity in S-41

Yrast states in the neutron-rich S-41 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S-36 ions with a thin Pb-208 target. The magnetic spectrometer, PRISMA, and the gamma-ray array, CLARA, were used in the measurements. gamma-ray transitions of energy 449 and 638 keV were observed. Results from published intermediate-energy Coulomb excitation measurements in combination with those from the present work have led to the construction of a new S-41 level scheme. Proposed J(pi) values are based on experimental observation and on model-dependent arguments. The level scheme and published electromagnetic transition probabilities are discussed within the context of state-of-art shell-model calculations using the SDPF-U effective interaction. In contrast with the excellent agreement observed in earlier published work, here there are significant discrepancies between experiment and the results of shell-model calculations.