Ionization, excitation, and chemical reaction in uniform electric fields I―The Townsend coefficient of ionization

Abstract

The development of a complete theory of the relationship between the data concerning single impacts of electrons on gas molecules (or atoms) and the average properties of electron swarms in gases, of which the Townsend coefficient of ionization is one, is beset with grave difficulties, It is ideally possible to predict this relationship from a knowledge of the scattering of individual electrons in collision; there are, however, neither sufficient data available from scattering experiments nor is the corresponding theory of scattering adequately developed. The method of discussing the experimental data to be developed in this paper does not go so deeply into the problem. For the particular case of ionization by electron impact it attempts to find what auxiliary data are necessary to reveal the inter-relation between certain average properties of electron swarms in gases, and their relation to data concerning single impacts between electrons and gas molecules (or atoms) which result in ionization. It is found that the only auxiliary data necessary for this purpose are those describing the electron velocity distribution in the swarm for which the average properties have been measured.