Diffusion of xenon in liquid alkanes: Temperature dependence measurements with a new method. Stokes–Einstein and hard sphere theories

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Abstract
Measurements are reported of the diffusion constant D(T) for xenon gas, in the form of the radioisotope 133Xe, through liquid n-octane, n-decane, and n-tetradecane, in the range 10–40 °C. The values range from D (10.0 °C, Xe→n-C14H30)=1.32×10−5 cm2/s to D (40.0 °C, Xe→n-C8H18)=6.02×10−5 cm2/s. A new experimental method is used in which D is obtained by monitoring the decrease in concentration as gas diffuses into the liquid in an effectively one-dimensional geometry. As expected, the results do not agree with the Stokes–Einstein law. They do follow the usual correlation Dηp=AT, with p=0.708 and A=9.80×10−8, where η is the liquid viscosity in centipoises and T is in K. Application to these results of the rough-hard-sphere theory of diffusion is discussed. A quantitative analysis cannot be made until molecular dynamics results for smooth-hard-sphere diffusion are available.