Measurements of 31S energy levels and reevaluation of the thermonuclear resonant 30P(p, γ)31S reaction rate

By measuring the P-31(He-3, t)S-31, P-31(He-3, t)S-31*(p)P-30, and S-32(d, t)S-31 reactions, the level scheme of S-31 has been refined and extended up to E-x = 9.5 MeV. A total of 17 new levels, and 5 tentative new levels, have been measured. In addition, 5 tentatively known levels have been confirmed. The uncertainties in the excitation energies of many known S-31 levels have been reduced substantially. Spin constraints have been made for 8 proton-unbound levels by measuring 18 triton-proton angular correlations from the P-31(He-3, t)S-31*(p)P-30 reaction. Finite proton-decay branching ratios (including discrimination between decays to the ground state and first two excited states of P-30) have been measured for 38 levels, and upper limits have been set for 3 additional levels. The lowest isospin T = 3/2 level has been observed, and candidates for the second and third T = 3/2 levels have been identified. The new experimental information on P-30 + p resonance parameters has been used together with data from previous measurements to calculate the thermonuclear, resonant P-30(p, gamma)S-31 reaction rate over three orders of magnitude in temperature: 0.01 < T < 10 GK. Good agreement is found with estimates based on Hauser-Feshbach statistical models over the range 0.08 < T < 10 GK, but differences are found with rates previously estimated using the experimental information at hand.