On the semiclassical impulse approximation for electron capture in assymetric ion-atom collisions

A derivation of the impulse approximation for the capture ofa target K-shell electron by a light projectile in ion-atom collisions is given in the framework of the semiclassical approximation. The impact-parameter dependence of the capture probability is calculated numerically without further approximations, and shows good agreement with recent experimental results for protons colliding with Ne and Ar. The validity of several peaking approximations and the relation to ionisation theories are briefly discussed. (Auth.)