Motion of Gaseous Ions in a Strong Electric Field. II

Abstract

This paper continues an earlier one on the same subject. Its object is to elucidate the nature of the random motion of an ion about its drift. In Sec. F it is shown that this motion can be described as a diffusion with a diffusion tensor axially symmetric about the field. If the mean free time between the collisions of an ion with molecules is independent of speed, then explicit expressions may be deprived for the two diffusion coefficients; these expressions are written down without proof in Sec. G; they are connected with the mobility by a natural extension of the Einstein relation. In Sec. H, the longitudinal diffusion coefficient is computed numerically for the hard sphere model, high field, and mass ratio 1; the method of computation is the same as in Sec. D. Finally, it is shown in Sec. I how approximate formulas of wider validity can be inferred from the ones obtained.