Unbound states of 32Cl and the 31S(p,\gamma)32Cl reaction rate

TL;DR

This paper investigates the unbound states of 32Cl to refine the 31S(p,)32Cl reaction rate, crucial for understanding nova nucleosynthesis and sulfur enrichment, by experimental measurements of charge-exchange reactions and decay properties.

Contribution

It provides new experimental data on 32Cl unbound states and improves the reaction rate calculation with quantified uncertainties.

Findings

Identified key unbound states in 32Cl affecting the reaction rate

Measured proton-branching ratios of 32Cl states

Produced an improved, uncertainty-quantified 31S(p,)32Cl reaction rate

Abstract

The 31S(p,\gamma)32Cl reaction is expected to provide the dominant break-out path from the SiP cycle in novae and is important for understanding enrichments of sulfur observed in some nova ejecta. We studied the 32S(3He,t)32Cl charge-exchange reaction to determine properties of proton-unbound levels in 32Cl that have previously contributed significant uncertainties to the 31S(p,\gamma)32Cl reaction rate. Measured triton magnetic rigidities were used to determine excitation energies in 32Cl. Proton-branching ratios were obtained by detecting decay protons from unbound 32Cl states in coincidence with tritons. An improved 31S(p,\gamma)32Cl reaction rate was calculated including robust statistical and systematic uncertainties.