Improving the P30(p,γ)S31 rate in oxygen-neon novae: Constraints on Jπ values for proton-threshold states in S31

Calculation of the thermonuclear {sup 30}P(p,{gamma}){sup 31}S rate in oxygen-neon nova explosions depends critically upon nuclear structure information for states within {approx}600 keV of the {sup 30}P+p threshold in {sup 31}S. We have studied the {sup 31}P({sup 3}He,t){sup 31}S reaction at 25 MeV using a high-resolution quadrupole-dipole-dipole-dipole magnetic spectrograph. Tritons corresponding to the states E{sub x}({sup 31}S) {approx} 6.1-7.1 MeV were observed at ten angles between {theta}{sub lab} = 10 deg. and 55 deg. States that were only tentatively identified in past studies have been observed unambiguously. For the first time, we have measured and analyzed angular distributions of the {sup 31}P({sup 3}He,t){sup 31}S reaction. We present, also for the first time, a consistent set of experimental spin constraints for all except one of the critical proton-threshold states in {sup 31}S. Hydrodynamic nova simulations have been calculated in order to assess the impact on nova nucleosynthesis of remaining uncertainties in J{sup {pi}} values of {sup 31}S states and the unknown relevant proton spectroscopic factors. We find that these uncertainties may lead to a factor of up to 20 variation in the {sup 30}P(p,{gamma}){sup 31}S rate over typical nova peak temperatures, which may then lead to a factor of up tomore » 4 variation in the nova yields of Si-Ar isotopes.« less