Molecular Dissociation by Electron Impact

Abstract

ABOUT two years ago I noticed¹ that the positive ions generated along the path of an electron beam nearly all came out of the electron beam at right angles to it with energies of the order of 1 or 2 volts, that is, considerably higher than their thermal energies. I found that this was due to a radial potential gradient being set up around the electron beam by concentration gradients in the electron gas surrounding the beam. The presence of these radial potential gradients would introduce considerable difficulties into the accurate measurement of the kinetic energies of the dissociation products formed by electron impact in a molecular gas, for the dissociation products possess energies of only the same order of magnitude as the energy gained in falling through the potential gradient set up by the electron beam.