Toward concordance of Ex and JPi values for proton unbound 31S states

Nucleosynthesis in classical novae on oxygen-neon white dwarfs is sensitive to the poorly constrained thermonuclear rate of the 30P(p,¿)31S reaction. In order to improve this situation, a variety of experiments have been performed over the past decade to determine the properties of proton unbound 31S levels up to an excitation energy of ˜6.7 MeV. Inconsistencies in the energies and Jp values for these levels have made it difficult to produce a useful 30P(p,¿)31S reaction rate based on experimental information. In the present work, we revisit a subset of published data on the structure of 31S in order to shed light on these problems. First, we present an alternative calibration of 31P(3He, t)31S spectra using newly available high-precision data in order to address discrepant 31S excitation energies. Second, we apply a similar method to a recently acquired 32S(d, t)31S spectrum. Third, for a different 31P(3He, t)31S experiment in which angular distributions were acquired, we present alternative fits to the experimental data in order to address discrepant 31S Jp values. Finally, we compare the Jp values from 31P(3He, t)31S to those reported from in beam ¿-ray spectroscopy experiments in order to search for potential resolutions to the inconsistencies. Overall, viable new solutions to some of the problems emerge, but other problems persist.
Peer Reviewed
Postprint (author's final draft)