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

By measuring the ³¹P(³He,t)³¹S, ³¹P(³He,t)³¹S^*(p)³⁰P, and ³²S(d,t)³¹S reactions, the level scheme of ³¹S 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 ³¹S levels have been reduced substantially. Spin constraints have been made for 8 proton-unbound levels by measuring 18 triton-proton angular correlations from the ³¹P(³He,t)³¹S^*(p)³⁰P reaction. Finite proton-decay branching ratios (including discrimination between decays to the ground state and first two excited states of ³⁰P) 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 ³⁰P+p resonance parameters has been used together with data from previous measurements to calculate the thermonuclear, resonant ³⁰P(p,γ)³¹S 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.