Isotopic Thermal-Diffusion Factor for Xenon

The isotopic thermal-diffusion factor α0 for xenon has been determined over a mean temperature range of 245° to 543°K. An artificial mixture of xenon isotopes containing approximately 18% 129Xe and 15% 136Xe was subjected to thermal diffusion in a 10-tube swing separator; the isotopic thermal-diffusion factor was obtained from the change of concentrations of these two isotopes only. A best-fitting procedure yields potential parameters α=16 and ε/k=257°K for the exponential-six interaction-potential model, whereas the Lennard-Jones (12:6) model fails to reproduce the experimental results. This exp-6 potential was then used to calculate the values of diffusion, viscosity, thermal conductivity, and second virial coefficient, and a reasonably good agreement was obtained with rm=4.41 Å. An intercomparison of the observed and the theoretically calculated isotopic thermal-diffusion factors for all the inert gases from T*=0.6 to 60 is also presented.