Anisotropic Diffusion in Electron Swarms

Abstract

We show that the distribution functions derived by Parker (1963) in his analysis of the TownsendHuxley experiment can be used to calculate DL/D, the ratio of longitudinal to isotropic diffusion coefficients for electron swarms in electrostatic fields in gases. In the case of a constant collision frequency interaction our results agree with previous calculations, whilst for a constant mean free path we find DL/D = 0·58. This result is some 16% higher than previously published values but provides better agreement with experiment for electrons in helium.