Intermolecular Forces: Thermal Diffusion and Diffusion in He-Kr and H2-Kr

Forces between unlike molecules are investigated via mutual and thermal diffusion measurements on 4He-85Kr and H2-85Kr. New experimental results are reported, the thermal diffusion measurements covering the temperature range 77 to 760°K. Above 300°K the measurements are in reasonable accord with those of Ghozlan and Kistemaker, but below 300°K there are substantial discrepancies. Evidence is presented which indicates that the previous results at the lowest temperatures, particularly for He-Kr, are incorrect. Present measurements support the adequacy of the common potential parameter combination rules for H2-Kr, but not for He-Kr; in the latter case the potential well depth ε12is apparently smaller than theoretically predicted, a conclusion in accordance with molecular-beam scattering measurements.