Astrophysical S-Factors from Asymptotic Normalization Coefficients

Abstract

Peripheral transfer reactions can be used to determine asymptotic normalization coefficients (ANC). These coefficients, which provide the normalization of the tail of the overlap function, determine S-factors for direct capture reactions at astrophysical energies. A variety of proton transfer reactions have been used to measure ANCs. As a test of the technique, the 16 O(3He,d)17 F reaction has been used to determine ANCs for transitions to the ground and first excited states of 17 F. The S-factors for 16 O(p,γ)17 F calculated from these 17 F → 16 O +p ANCs are found to be in very good agreement with recent measurements. Following the same technique, the 10 B(7 Be,8 B)9 Be and 14 N(7 Be,8 B)13 C reactions have been used, along with optical model parameters for the radioactive beams that were obtained from a study of elastic scattering of loosely bound p-shell nuclei, to measure the ANC appropriate for determining 7 Be(p,γ)8 B. The results from the two transfer reactions provide an indirect determination of S 17(0). Recent measurements have been completed on the 14 N(11 C, 12 N)13 C reaction which will allow us to define the astrophysical S-factor for the 11 C(p,γ)12 N reaction.