Unified Faddeev treatment of high-energy electron capture

A second-order Faddeev scattering formalism is developed for treating high-energy electron capture in nonrelativistic ion-atom collisions. The approximation to the exact capture amplitude encompasses both forward-angle and large-angle scattering. Comparison with forward-angle experimental data for protons on hydrogen and helium at energies of a few MeV shows very good agreement. The contribution of the internuclear potential to the amplitude is analyzed, and an explicit explanation of its effects as described by the eikonal transformation is given in a multiple-scattering approach. The amplitude is shown to be well behaved for singly charged incident ions.