Collectivity in ⁴¹S

Yrast states in the neutron-rich ⁴¹S nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of ³⁶S ions with a thin ²⁰⁸Pb target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. γ-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 ⁴¹S level scheme. Proposed Jπ 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.