Astrophysical factor for the neutron generator 13C(alpha,n)16O reaction in the AGB stars

/ Authors

E. Johnson, G. Rogachev, A. Mukhamedzhanov, L. Baby, S. Brown, W. Cluff, A. Crisp, E. Diffenderfer, V. Goldberg, B. W. Green

and 8 more authors

T. Hinners, C. Hoffman, K. Kemper, O. Momotyuk, P. Peplowski, A. Pipidis, R. Reynolds, B. Roeder

/ Abstract

The reaction 13C(alpha,n) is considered to be the main source of neutrons for the s-process in AGB stars. At low energies the cross section is dominated by the 1/2+ 6.356 MeV sub-threshold resonance in 17O whose contribution is determined with a very large uncertainty of ~1000% at stellar temperatures. In this work we performed the most precise determination of the low-energy astrophysical S factor using the indirect asymptotic normalization (ANC) technique. The alpha-particle ANC for the sub-threshold state has been measured using the sub-Coulomb alpha-transfer reaction (6Li,d). Using the determined ANC we calculated S(0), which turns out to be an order of magnitude smaller than in the NACRE compilation.