The C-12(alpha,gamma)O-16 reaction at astrophysical energies

The experimental measurement of the C-12(alpha,gamma)O-16 reaction cross se ction is not feasible bellow a few MeV and so the determination of the S(E) factor at astrophysical energies (E-0=0.3 MeV) must be done through indire ct methods. These should consider the level structure of O-16, namely the 1 (-) and 2(+) resonances at 9.59 MeV and 9.85 MeV, that dominate the elastic and capture cross sections at the energies covered by experimental data, a nd the 1- and 2+ subthreshold states at 7.12 MeV and 6.92 MeV.