Toward concordance of $E_{x}$ and $J^{\pi}$ values for proton unbound ³¹S states

Abstract.

Nucleosynthesis in classical novae on oxygen-neon white dwarfs is sensitive to the poorly constrained thermonuclear rate of the ³⁰ P(p,$\gamma$)³¹ S 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 $\approx 6.7$ MeV. Inconsistencies in the energies and $J^{\pi}$ values for these levels have made it difficult to produce a useful ³⁰ P(p,$\gamma$)³¹ S 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 ³¹ P(³ He, t)³¹ S 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 ³² S(d, t)³¹ S spectrum. Third, for a different ³¹ P(³ He, t)³¹ S experiment in which angular distributions were acquired, we present alternative fits to the experimental data in order to address discrepant ³¹S $J^{\pi}$ values. Finally, we compare the $J^{\pi}$ values from ³¹ P(³ He, t)³¹ S to those reported from in beam $\gamma$-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.