Collisional detachment cross sections for H^-and He^-at high energies

Abstract

The single- and double-electron-loss cross section for H- and He- ions passing through H2, He, N2, Ne and Ar gas targets have been studied in the energy range 50-500 keV for H- impact and 100 keV-3 MeV for He- impact. H- and He- ions were formed from H+ and He+ by charge transfer in a gas cell and the cross sections were determined by the initial-growth method. The experimental cross sections for single-electron loss are compared with theoretical estimates, based upon the semi-empirical impulse approximation of Bates and Walker (1967). A comparison of the experimental results for H- and those for He- impact at equal impact velocities indicates an error of up to 50% in the basic, non-empirical part of the Bates-Walker theory.