One- and two-electron-loss cross sections from fast He-ions in hydrogen, helium and argon

The single- and double-electron-loss cross section for He- ions passing through H2, He and Ar gas targets have been studied in the impact-energy range from 100 keV to 3 MeV. He- ions were formed from He+ by charge transfer in a gas cell and the cross sections were determined by the initial-growth method. The experimental results for single-electron loss are compared with theoretical estimates based upon the semi-empirical classical impulse approximation of Bates and Walker (1966). For H2 and Ar targets, theory and experiment agree well within experimental error while the present results for He targets are 20% higher than the theoretical values.