S30studied with theS32(p,t)S30reaction and theP29(p,γ)S30reaction rate

Abstract

The $^{29}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{30}\mathrm{S}$ 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 $^{30}\mathrm{S}$ proton threshold at 4399 keV. To better understand the $^{29}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{30}\mathrm{S}$ rate, we have studied the $^{30}\mathrm{S}$ nucleus with the $^{32}\mathrm{S}$($p,t$)$^{30}\mathrm{S}$ reaction. We have observed 13 $^{30}\mathrm{S}$ 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 $^{29}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{30}\mathrm{S}$ reaction rate is approximately six times larger at nova temperatures than previously thought.