RECENT RESULTS FOR PROTON CAPTURE S FACTORS FROM MEASUREMENTS OF ASYMPTOTIC NORMALIZATION COEFFICIENTS

Abstract

Asymptotic normalization coefficients (ANCs) have proven to be useful for determining reaction rates of interest in nuclear astrophysics. These coefficients, which provide the normalization of the tail of the overlap function, determine 5' factors for direct capture reactions at astrophysical energies. They also can be related to resonance capture rates and are particularly useful for determining proton-capture reaction rates that involve subthreshold resonance states. Dnring the past eight, years, many ANCs have been measured by peripheral transfer reactions. Recent proton transfer reaction measurements have yielded ANCs for 1 4 0 --f 13N + p , 150 + 14N + p and Na + Ne + p . These results have been used to find S factors for 13N(p,7)140, l4N(p,7)l50 and 20Ne(p,7)21Na. Using mirror symmetry, the 13C('Li,8Li)'2C reaction has been used to obtain a new measurement of the ANC that defines the S factor for 7Be(p, Y ) ~ B . Following an introduction to ANCs, the recent experiments are discussed along with the astrophysical implications of these measurements.