Temperature Dependence of the Thermal Diffusion Factor for Helium, Neon, and Argon

Abstract

The isotopic thermal diffusion factor for He, Ne, and Ar has been measured by an all‐glass ``swing separator'' with its lower tube ends at 78° and 195°K, extending the temperature range of earlier data. These new data, along with the older ones, have been interpreted in terms of the L‐J (12–6) and modified exp‐six potentials. Various equilibrium and nonequilibrium properties are calculated and compared with the experimental data. An equation has been developed which relates the thermal diffusion factor with the absolute values of the viscosity, diffusion coefficient, and their derivatives and is essentially independent of the nature of intermolecular force. The thermal diffusion values are consistent with the available experimental data of viscosity and diffusion, through the use of the proposed relation, but more accurate data on diffusion as a function of temperature are needed for a precise evaluation. Approximate calculations are given to estimate the quantum corrections for He at 78° and 195°K.