Validity of the effective temperature scale for a dilute Li+ swarm in a Xe gas.

Abstract

The effective-temperature concept arising from the two-temperature (2T) kinetic theory for the nonreactive migration of a dilute ion swarm in a neutral gas under the action of a uniform electrostatic field has been tested over a wide temperature range by Monte Carlo simulation (MCS). Such a test over the prescribed temperature span has not been made experimentally because of the inherent difficulty in designing an apparatus which permits the temperature of the ion drift chamber to be varied so widely. The MCS test is here applied to ${\mathrm{Li}}^{+}$ in Xe, which offers the most favorable conditions for the 2T theory to be a valid approximation of the more sophisticated three-temperature theory. Results established that for such cases it is possible to express the mobility ${\mathit{K}}_{0}$ and transverse diffusion ${\mathit{D}}_{\mathit{T}}$, but not the longitudinal diffusion ${\mathit{D}}_{\mathit{L}}$, in terms of a univariate effective-temperature scale instead of the separate parameters of gas temperature and the ratio of electric field to gas concentration. More remarkably, the ratio ${\mathit{D}}_{\mathit{T}}$/K was found to bear a simple linear relation with ${\mathit{T}}_{\mathit{e}\mathit{f}\mathit{f}}$ over a very wide range.