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The rate of the 25 Al(p, γ ) 26 Si reaction is one of the few key remaining nuclear uncertainties required for predicting the production of the cosmic γ -ray emitter 26 Al in explosive burning in novae. This reaction rate is dominated by three key resonances ( J π = 0 + , 1 + and 3 + ) in 26 Si. Only the 3 + resonance strength has been directly constrained by experiment. A high resolution measurement of the 25 Mg(d, p) reaction was used to determine spectroscopic factors for analog states in the mirror nucleus, 26 Mg. A first spectroscopic factor value is reported for the 0 + state at 6.256 MeV, and a strict upper limit is set on the value for the 1 + state at 5.691 MeV, that is incompatible with an earlier ( 4 He, 3 He) study. These results are used to estimate proton partial widths, and resonance strengths of analog states in 26 Si contributing to the 25 Al(p, γ ) 26 Si reaction rate in nova burning conditions. [ABSTRACT FROM AUTHOR]

The structure of proton-unbound 30S states strongly determines the thermonuclear 29P(p,γ)30S reaction rate at temperatures characteristic of explosive hydrogen burning in classical novae and type I x-ray bursts. Specifically, the rate had been previously predicted to be dominated by two low-lying, unobserved, levels in the Ex= 4.7-4.8 MeV region, with spin and parity assignments of 3+ and 2+. In recent experimental work, two candidate levels were observed with energies of 4.699 MeV and 4.814 MeV, but no experimental information on their spins and parities was obtained. We have performed an in-beam γ-ray spectroscopy study of 30S with the 28Si(3He, nγ)30S reaction. By constructing the decay schemes of proton-unbound states with a γ-γ coincidence analysis of their decay γ rays, their Jπ values were inferred from a comparison to the known decay schemes of the corresponding mirror states in 30Si. For the two aforementioned states, our results strongly corroborate the spin-parity assignments assumed in recent evaluations of the 29P(p,γ)30S reaction rate. [ABSTRACT FROM AUTHOR]