Diffusion in Lorentzian and quasi-Lorentzian N2-light noble gas mixtures

Abstract

Abstract Mutual diffusion coefficients as a function of temperature have been measured for N2-light noble gas (He and Ne) mixtures in the temperature range of 212–445 K with either component in trace concentration. The accuracy of the measurements is 1–2 part per mil. The present studies support the adequacy of theoretically linking the logarithmic temperature derivative of the diffusion coefficient, (∂ ln D/∂ ln T)p, with thermal diffusion data in order to determine the influence of rotational collisions on ( 6C ∗ −5 ) and ( 6 C −5 ). For the system He−N2 the value of Zrot obtained from the latter is in excellent agreement with the directly measured value. The results show that for the two mixtures, Zrot≈5 (Ne) and 9 (He), the efficiency of translational-rotational energy transfer is small. The results indicate that the relation between Zrot and ( 6 C −5 ), valid for the loaded-sphere model, is in close agreement with experiment for large T∗ values, typically T ∗ ⩾5 . The experimental ( 6C ∗ −5 ) values are in better agreement with the corresponding ones of the exp-6 model with steepness 14 than for a Lennard-Jones potential or exp-6–15.