Analysis of presolar grains in primitive meteorites has shown isotopic ratios largely characteristic of the conditions thought to prevail in various astrophysical environments. A possible indicator for a grain of ONe nova origin is a large ${}^{33}\mathrm{S}$ abundance: nucleosynthesis calculations predict as much as 150 times the solar abundance of ${}^{33}\mathrm{S}$ in the ejecta of nova explosions on massive ONe white dwarfs. This overproduction factor may, however, vary by factors of at least 0.01–3 because of uncertainties of several orders of magnitude in the ${}^{33}\mathrm{S}$$(p,\gamma )$${}^{34}\mathrm{Cl}$ reaction rate at nova peak temperatures ($T_{\mathrm{peak}}~0.1\text{−}0.4$ GK). These uncertainties arise due to the lack of nuclear physics information for states within $~600$ keV of the ${}^{33}\mathrm{S}$$+p$ threshold in ${}^{34}\mathrm{Cl}$ (S${}_p$(${}^{34}\mathrm{Cl}$) = 5143 keV). To better constrain this rate we have measured, for the first time, the ${}^{34}\mathrm{S}$(${}^3\mathrm{He}$,$t$)${}^{34}\mathrm{Cl}$ reaction over the region $E_x$(${}^{34}\mathrm{Cl}$) = 4.9–6 MeV. We confirm previous states and find 15 new states in this energy region. New ${}^{33}\mathrm{S}$$(p,\gamma )$${}^{34}\mathrm{Cl}$ resonances at $E_R=281(2)$, 301(2), and 342(2) keV may dominate this rate at relevant nova temperatures. Our results could affect predictions of sulphur isotopic ratios in nova ejecta (e.g., ${}^{32}\mathrm{S}$/${}^{33}\mathrm{S}$) that may be used as diagnostic tools for the nova paternity of grains.

• Received 11 May 2009

DOI:https://doi.org/10.1103/PhysRevC.80.015802