beta-Delayed alpha Decay of N-16 and the C-12(alpha,gamma)O-16 Cross Section at Astrophysical Energies: a New Experimental Approach

Abstract

The C-12(alpha,gamma)O-16 reaction at energies corresponding to the quiescent helium burning in massive stars is regarded as one of the most important processes in nuclear astrophysics. Although this process has being studied for over four decades, our knowledge of its cross section at the energies of interest for astrophysics is still widely unsatisfactory. Indeed, no experimental data are available around 300 keV and in the energy region of astrophysical interest extrapolations are performed using some theoretical approaches, usually R-matrix calculations. Consequently, the published astrophysical factors range from 1 to 288 keVb for S-E1(300) and 7 to 120 keVb for S-E2(300), especially because of the unknown contribution coming from subthreshold resonances. To improve the reliability of these extrapolations, data from complementary experiments, such as elastic and quasi-elastic alpha scattering on C-12, alpha-transfer reactions to O-16, and N-16 decay are usually included in the analysis. Here the beta-delayed alpha decay of N-16 is used to infer information on the C-12(alpha,gamma)O-16 reaction and a new experimental technique is suggested.