Unbound states of \u3csup\u3e32\u3c/sup\u3eCl and the \u3csup\u3e31\u3c/sup\u3eS(p,γ) \u3csup\u3e32\u3c/sup\u3eCl reaction rate

The 31S(p,γ)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,γ)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,γ)32Cl reaction rate was calculated including robust statistical and systematic uncertainties. © 2011 American Physical Society