A new $^{30}$P(p,$\gamma$)$^{31}$S reaction rate and its astrophysical implications

The $^{30}$P(p,$\gamma$)$^{31}$S reaction rate plays a crucial role in the synthesis of heavier elements in ONe nova outbursts. However, this rate is very uncertain due to the lack of spectroscopic information on the $^{31}$S levels. We have measured differential cross sections for the $^{32}$S(p,d)$^{31}$S reaction and determined excitation energies for 26 states in $^{31}$S. Spins and parities were determined or constrained for strongly populated levels through a DWBA analysis. A total of 42 levels in $^{31}$S were examined. A new $^{30}$P(p,$\gamma$)$^{31}$S rate was calculated using this new resonance information. Our results indicate that the $^{30}$P(p,$\gamma$)$^{31}$S rate is reduced by up to a factor of 10 at nova temperatures compared to an estimate made with a statistical reaction model. We have performed network calculations using the new rate. Production of elements in the Si-Ca region are found to be altered by as much as 30\%. Important isotopic ratios such as $^{12}$C/$^{13}$C, $^{14}$N/$^{15}$N, $^{26}$Al/$^{27}$Al and $^{29,30}$Si/$^{28}$Si are found to agree well with observations on presolar grains of nova origin.