Angular asymmetry of low-energy electron emission in ion-atom collisions

We show that two factors contribute to the forward-backward angular asymmetry in low-energy electron emission by ion impact: the deviation of the target potential from a pure Coulomb potential and the two-center effect. We perform calculations with various theories that include these two effects: the continuum-distorted-wave--eikonal-initial-state (CDW-EIS) and the CDW approximations based on distorted-wave perturbation theory and a close-coupling calculation using a discrete representation of the continuum. The various theories give consistent results on the asymmetry but discrepancies remain between theory and experiment. {} 1996 The American Physical Society.