Intermolecular forces in mixtures of helium with the heavier noble gases

Abstract

Crossed beams differential scattering cross sections have been measured for HeAr, HeKr, and HeXe with a new beam modulation technique at two energies. Interatomic potential functions have been found which describe both scattering and dilute gas bulk properties for these systems. Potential functions independently determined from gas phase bulk properties are shown to give a very good account of the scattering data. The potential well depth is found to be about equal for the three systems, in agreement with Chen et al. [J. Chem. Phys. 59, 601 (1973)], although our values are in average 17% larger than those found in the cited work. Also, the deviations of the three potentials from a common shape are smaller than those found by Chen et al. The ability of combining rules to predict the mixed interaction from a knowledge of the pure gas interactions is tested. In contrast to some of the previous work in the field, we conclude that simple combining rules can be found that give useful predictions.