On the question of the well depth of the He–Ar interatomic potential

Abstract

New, high resolution, differential collision cross section data for the scattering of He by Ar atoms, obtained in Göttingen, are found to be inconsistent with the predictions derived from a recently proposed He–Ar potential [M. Keil et al., J. Chem. Phys. 70, 482 (1979)] and confirm previous work by K. M. Smith et al. [J. Chem. Phys. 67, 152 (1977)]. It is shown that the He–Ar well depth is 29.4 K (accurate to 5% and 44% larger than the value of Keil et al.), independent of the parametrization of the potential. A careful analysis of the bulk properties of the He–Ar mixture also shows that the attractive part of the potential proposed by Keil et al. is too weak. A potential of the SPFD form is presented which is able to reproduce the best data for the differential cross section, the second virial coefficient, the diffusion and viscosity within the quoted experimental errors.