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 r_m=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.