Excitation Probabilities for Electrons in Helium, Neon, and Argon

Abstract

Electrons scattered inelastically in the forward direction in helium, neon, and argon have been studied by means of an electrostatic analyzer. Energy distribution curves revealed the 21.11 and 22.96 volt losses in helium, the 16.6 and 18.5 volt losses in neon, and the 11.6 and 13.9 volt losses in argon. Careful measurements of the principal energy losses gave 21.13 +.04 volts, 16.64 + .05 volts, and 11.53+ .05 volts. The relative probability as a function of electron energy was determined for the 21.11, 16.6, and 11.6 volt losses for electron energies between 100 and 300 volts. The 21.11 and 16.6 volt losses increased with electron energy showing maxima at 200 and 160 volts respectively. The 11.6 volt loss decreased sharply between 100 and 150 volts and then remained constant. Special study of ionization losses in helium showed that an ionizing electron may lose as much as half its remaining energy to the ejected electron, but that smaller losses are preferred.