A survey of electron swarm data

Abstract

An electron swarm consists of a small number density n of electrons in a gas of much higher number density N. The mean energy and energy distribution of such a swarm are determined by the value of E/N where E is the electric field. At any given value E/N the swarm may be characterized by the values of eight parameters, viz; drift velocity, diffusion coefficient. (diffusion coefficient/mobility, excitation coefficient, electron attachment coefficient, electron detachment coefficient, ionization coefficient, recombination coefficient. In this survey, data on these parameters obtained by a variety of experimental techniques are collected, discussed, and compared graphically. Also included on the graphs are computed values of the parameters obtained in many cases from cross sections and energy distributions chosen to give the best fit with the swarm data. Selected tabulations of the data are also given except in cases for which the accuracy of the data is not sufficient to warrant numerical presentation. The mean energy of the electron swarms ranges from thermal to several electron volts and the gases for which data are given are the rare gases, the common molecular gases (H2, N2, O2, CO, NO, CO2, NO2) and air. The survey also contains an extensive bibliography which includes references (i) to publications on electron swarms in a much wider range of gases than those for which data are given and (ii) to papers concerned with energy distributions, conductivity and ionization coefficients in crossed electric and magnetic fields in addition to those relating to the eight parameters listed above.