Revised result for theCl32(p,γ)Ar33reaction rate for astrophysicalrp-process calculations

Abstract

The $^{32}\mathrm{Cl}$(p,\ensuremath{\gamma})$^{33}\mathrm{Ar}$ reaction rate is of potential importance in the rp process powering type I x-ray bursts. Recently, Clement et al. [Phys. Rev. Lett. 92, 172502 (2004)] [1] presented new data on excitation energies for low-lying proton unbound states in $^{33}\mathrm{Ar}$ obtained with a new method developed at the National Superconducting Cyclotron Laboratory. We use their data, together with a direct capture model and a shell model calculation, to derive a new reaction rate for use in astrophysical model calculations. In particular, we take into account capture on the first excited state in $^{32}\mathrm{Cl}$, and we also present a realistic estimate of the remaining uncertainties. We find that the $^{32}\mathrm{Cl}$($p,\ensuremath{\gamma}$)$^{33}\mathrm{Ar}$ reaction rate is dominated entirely by capture on the first excited state in $^{32}\mathrm{Cl}$ over the whole temperature range relevant in x-ray bursts. In the temperature range from 0.2 to 1 GK the rate is up to a factor of 70 larger than the previously recommended rate based on shell model calculations only. The uncertainty is now reduced from up to a factor of 1000 to a factor of 3 at 0.3--0.7 GK and a factor of 6 at 1.5 GK.