Comparative studies of the nonlinear effects occurring when highly charged projectiles collide with hydrogen, a free electron gas, and a harmonic oscillator

Abstract

We calculate the nonlinear effects that appear at the level of the stopping cross section when heavy bare projectiles collide with both atomic hydrogen and a free electron gas. Calculations are carried out by using distorted-wave methods. For hydrogen targets we employ the continuum-distorted-wave eikonal initial-state approximation, while for the free electron gas we use the Coulomb-Lindhard approach. Results are compared with exact results for the quantum harmonic oscillator target. Ratios to the first-order stopping are analyzed in detail and their structures are interpreted in terms of Padé approximants. We also investigate the dependency of the stopping ratios on the impact parameter.