SIMPLE APPROXIMATION FOR THERMAL-DIFFUSION IN IONIZED-GAS MIXTURES

A simple approximation for thermal diffusion in gas mixtures was recen tly proposed [1]. This approximation was based upon relations valid fo r rigid spheres. It is therefore appropriate for molecules with steep repulsive potentials, but not for ionized species interacting via the Coulomb potential. Here we formulate an analogous approximation for io nized species and free electrons. The resulting thermal diffusion coef ficients differ in sign from those for hard molecules.