A quantum-mechanical approximation is developed for ionization of one-electron targets by charged-ion impact. The model is based on the nonrelativistic distorted-wave formalism valid for impact velocities larger than the electron orbital velocity in the initial state. The exact impulse wave function is used to describe the initial state, thus incorporating the projectile potential to all orders. The final state is represented by a product of continuum Coulomb wave functions around both centers, providing the correct asymptotic conditions and the projectile and target cusps. The theory is thought to be valid for large projectile charge, even larger than the ion velocity. The impulse approximation developed here is expensive in computing time, but it is probably one of the few models to deal with high projectile charges. Double-differential cross sections are computable in the forward and backward ejection angles. Comparisons with the experiments in different regions of interest are presented, including the binary sphere, capture to the continuum cusp, ridge electrons, and backward ejection angles. The theory proves to be quite successful, and it does not seem to deteriorate with increasing projectile charge.

• Received 30 January 1991

DOI:https://doi.org/10.1103/PhysRevA.43.5919