ANGULAR ASYMMETRY OF LOW-ENERGY-ELECTRON EMISSION IN ION-ATOM COLLISIONS

We show that two factors contribute to the forward-backward angular as ymmetry in low-energy electron emission by ion imp;act: the deviation of the target potential from a pure Coulomb potential and the two-cent er 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 perturbat ion theory and a close-coupling calculation using a discrete represent ation of the continuum. The various theories give consistent results o n the asymmetry but discrepancies remain between theory and experiment .