Single-electron loss by fast (0.02-4 MeV) helium atoms in H2 and He gases

The single-electron loss cross section for He atoms passing through H2 and He gas targets has been studied in the impact-energy range from 20 keV to 4 MeV. He atoms were formed by charge-transfer neutralization of He+ ions in a He gas. At low energies, the cross sections were determined by beam attenuation in a transverse electrostatic field and, at higher energies, by the initial-growth method. The results were compared with Born-approximation calculations, and good agreement was found at energies above 500 keV for He in H2 and above 1200 keV for He in He.