Free Path Formulae for the Coefficient of Diffusion D and Velocity of Drift W of Ions and Electrons in Gases

Abstract

In derivations of formulae for D and W for electrons by the method of free paths (Huxley 1957a, 1957b) the assumption was made that along a number of successive free paths an electron travels at essentially the same speed c. As this assumption is not true of ions it would not be legitimate to apply the formulae to the motion of ions in gases without further discussion. However, the formulae are in fact valid for ionic motion and in what follows they are established in a more general form.