Determination of ionization potentials. Part 1.—The use of theoretical expressions which incorporate the effects of Maxwellian inhomogeneity

Abstract

A study has been made of the feasibility of determining electron-impact ionization potentials by fitting various theoretical expressions to experimental ionization efficiency behaviour. The theoretical expressions which have been examined incorporate the effects of the Maxwellian energy distribution of a thermionic energy source, and are based on threshold behaviour proportional to the first or second power of the excess electron energy, and the occurrence of one or two ionization processes in the experimental potential range examined. The results indicate that first ionization potentials may be determined within an accuracy of ±0.3 eV, although the procedure in its present stage of refinement cannot be reliably extended to the determination of higher ionization potentials.