R-matrix Analysis of CNO Cycle Reactions

Abstract

A multi-channel R-matrix code has been developed and used to analyse two key reactions in the CNO cycle. The N-14(p,gamma)O-15 reaction determines the rate of operation of the CN cycle and is critical in determining the age of globular clusters, which give estimates for the age of the universe. The low energy S-factors determined are in good agreement with recent estimates. A preliminary analysis of the elastic scattering channel has shown that it may offer additional constraint on the radiative capture channels, though further analysis is required.

The N-15(p,gamma)O-16 and N-15(p,alpha)C-12 reactions are the branching point between the first and second CNO cycles and their relative reaction cross-sections determine the transit of catalytic material to higher cycles. The (p,alpha) astrophysical S-factor found is in very good agreement with recent estimates, but the (p,gamma) low energy S-factor is found to be lower than the most recently reported values.

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