Perturbation treatment of thermal motions in gaseous ion-transport theory

Abstract

Wannier's cold-gas ion-transport theory has been extended to finite gas temperature by the inclusion of thermal motions in a perturbation approach. The simplicity of the cold-gas collision integrals makes the use of very large basis sets feasible, and as a consequence very accurate calculations of the transport coefficients, over the range of electric fields where the perturbation theory gives convergent results, can be carried out. For light ions in a heavy gas, i.e. for non-neutral-atom mass ratios m/M<or approximately=0.25, convergent results are obtained for all values of the electric field, while for larger mass ratios the perturbation expansions diverge in the low-field range.