Self-Diffusion in Argon

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Abstract
The self-diffusion coefficient of argon was measured at five different temperatures between −183°C and 53.5°C by observing the diffusion of radioactive A41 into normal argon. The decrease in the observed diffusion coefficient caused by the larger mass of A41 was deduced and found to be 0.6 percent. The experimental values are compared with several theoretical calculations. In particular, it is shown that use for argon of an inverse power model (V ∝ r−ν), with different values of ν ascribed to different temperature ranges, is not permissible since widely different values of ν at the same temperature can be obtained from different experimental data. The experimental figures agree very well with numerical calculations by Hirschfelder, Bird, and Spotz based on an interaction potential of the form 4E[—(r0/r)6+(r0/r)12].