Determination of the subthreshold state contribution in C-13(alpha,n)O-16, the main neutron-source reaction for the s process

Abstract

The reaction rate of the stellar reaction C-13(alpha,n)O-16, which is currently considered to be the main neutron source for the slow (s) process at low energies, has been rederived using the direct alpha-transfer reaction C-13(Li-6,d)O-17 leading to the subthreshold state at 6.356 MeV in O-17. The contribution of the subthreshold state is found to be much smaller than the currently accepted predictions for the main neutron source of the s process, indicating less of a role of this reaction as the neutron source for the s-process scenario in low-mass stars at the asymptotic giant branch.