S30 studied with the S32(p,t)S30 reaction and the P29(p,γ)S30 reaction rate

The P29(p,γ)S30 reaction rate affects the interpretation of nova Si abundances, which have been precisely measured in presolar grains. The rate is thought to be dominated by previously unobserved 3⁺ and 2⁺ resonances above the S30 proton threshold at 4399 keV. To better understand the P29(p,γ)S30 rate, we have studied the S30 nucleus with the S32(p,t)S30 reaction. We have observed 13 S30 levels, nine of which are above the proton threshold, including a level at 4704 keV that is a candidate to be the important 3⁺ resonance. We also resolve a significant discrepancy between previously published excitation energies. From the observed triton angular distributions, we constrain the spins of several levels, ruling out several previous hypotheses and constraining some for the first time. Using our updated information, we estimate the P29(p,γ)S30 reaction rate is approximately six times larger at nova temperatures than previously thought.