Abstract
In nova outbursts on ONe White Dwarfs, the 30P(p,g)31S reaction plays a crucial role in the
synthesis of heavier nuclear species, from Si to Ca. However, this important rate is very uncertain
as a result of the lack of spectroscopic information on most of the levels above proton threshold in
31S. To reduce these uncertainties, we have measured differential cross sections for the 32S(p,d)31S
reaction and determined excitation energies for states in 31S. A total of 26 states in 31S were
observed, including 17 above the proton threshold. Five new states were observed. Spins and
parities were determined or constrained for 15 of the observed levels through a distorted wave Born
approximation (DWBA) analysis of the angular distributions, of which 6 were made for the first
time. We have evaluated 44 levels using existing data in combination with this measurement to
calculate a new 30P(p,g)31S reaction rate. We confirmed the spin-parity assignment of 1/2+ for the
state at 6263 keV which dominates the 30P(p,g)31S reaction rate at lower temperatures in novae,
while the state at 6544 keV dominates at temperatures above 0.2 GK. Our results indicate that
the 30P(p,g)31S rate is reduced by up to a factor of 10 at nova temperatures compared to previous
estimates.
