Electron Stripping of He and H in Helium, Hydrogen and Nitrogen Gases from 0.2 keV to 5.0 keV

The cross sections for electron stripping of fast helium atom in helium gas and in nitrogen gas have been measured by the initial-growth method. The observed values are considerably smaller than those obtained by Hayden and Utterback using the condenser method. The cross sections for hydrogen atom in hydrogen gas and in nitrogen gas have also been measured. Below 0.5 keV, the present results for the stripping cross sections differ from those obtained by other authors. This is attributed to the improper assumption adopted by these authors that the secondary electron emission coefficients for neutrals are equal to those for ions. These coefficients for neutral particles incident upon a copper surface have been experimentally determined in this work. The effect of re-neutralization and of scattering upon the apparent stripping efficiencies are discussed on the basis of the obtained cross sections for charge transfer and for elastic scattering.