Nonperturbative treatment of the screened-Coulomb contribution of projectile-electron loss

The electron-loss cross section of He+ ions impinging upon noble-gas targets (2 less than or equal to Z(2) less than or equal to 36) is calculated by using the coupled-channel method for the active projectile electron in the static screened field of the target atom. The calculations show a saturation of the projectile-electron-loss cross section with increasing target atomic number. This saturation effect due to neutral target systems is much more pronounced than for ionization or excitation by charged particles. Comparison with experimental data indicates a small electron-loss contribution from electron-electron interaction processes for heavy targets at intermediate velocities. Remaining discrepancies in the data are discussed in the light of the approximations involved in our theoretical treatment.