Calculation of the differential cross section for electron capture in fast ion-atom collisions

The approach to electron capture developed by Chan and Eichler is combined with the optical eikonal approximation for describing the effect of the internuclear potential on the projectile trajectory. In this way, a closed-form expression is derived for the differential cross section for 1s nlm capture. Numerical calculations have been performed for the reaction H++H(1s) H+H+ at collision energies of 25, 60, and 125 keV. Good agreement is obtained with the recent data of Martin et al. by using trajectories undeflected by the internuclear potential at small deflection angles and Coulomb-deflected trajectories at large deflection angles.