Behaviour of radiative-capture reactions near zero energy

Abstract

The Taylor expansion of the astrophysical S factor for radiative-capture reactions between charged particles is calculated in a direct way near zero energy in the potential and R matrix models. The 14 N(p, γ ) 15 O reaction is treated as an example. A similar expansion derived for neutron capture provides simple low-energy parametrizations of the 12 C(n, γ ) 13 C cross sections.