Asymptotic Normalization Coefficient and Important Astrophysical Process N-15(p, gamma)O-16
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In this work we report the application of the ANC method for the determination of the non-resonant radiative capture amplitude for the important astrophysical CNO cycle reaction 15N(p, ) 16O, which provides a leak from the CN cycle into the CNO bi-cycle and CNO tri-cycle. It is contributed by the resonance capture to the ground state through two strong 1- resonances and non-resonant capture to the ground state, which interferes with the resonant capture terms. To determine more accurately the contribution from the non-resonant capture we determined the proton ANCs for the ground and seven excited states of 16O by measuring the angular distributions of the peripheral 15N(3He, d)16O proton transfer reaction. Using these ANCs and proton and resonance widths determined from an R-matrix fit to the data from the 15N(p, )12C reaction, we calculated the astrophysical S factor for the 15N(p, )16O reaction. The results indicate that the direct capture contribution was previously overestimated. We find the astrophysical factor to be S(0) 36.0 6.0 keVb, which is about a factor of two lower than the presently accepted value. We conclude that for every 2200 300 cycles of the main CN cycle one CN catalyst is lost due to this reaction. 2010 IOP Publishing Ltd.
