Comment on a recent fast beam measurement of the electron impact ionisation cross sections of He, C, O and N atoms

Abstract

Recently Brook, Harrison and Smith (1978) reported a discrepancy between their electron impact ionisation cross sections for He at low electron energies, obtained with a fast atom beam technique, and data of Rapp and Englander-Golden (1965) who used a static gas target technique. They claim that this was due to an overestimation of the cross section by the static gas target technique. It is shown here, that this discrepancy can be explained by the uncertainty of the electron energy scale in the experiment of Brook et al.