Viscosity of ortho and para hydrogen mixtures

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Abstract
The viscosity of ortho-para hydrogen mixtures below 25 K is investigated for a model interaction chosen with an isotropic component that reproduces the high temperature viscosity and virial coefficient data and an anisotropic component inferred from rotation relaxation measurements. The T-matrix elements were calculated with a fast modification of the Numerov method and a close-coupled approximation adapted from the Arthurs-Dalgarno formalism. The model in itself could not explain the viscosity experiments of Becker and Stehl, but, when supplemented by dispersion forces dependent on the rotational state, proved to be satisfactory.