Anisotropic intermolecular forces

Abstract

Anisotropic intermolecular potentials for Ar · HF, Kr · HF and Xe · HF are obtained by least squares fitting to molecular beam spectra of van der Waals complexes. The absolute minimum is at the linear rare gas-HF geometry for all the systems considered. The potentials are reliable around the absolute minimum, but the existing data are not sensitive to the behaviour elsewhere. In particular, the absolute well depths and the behaviour around the linear rare gas-FH geometries are not well determined and depend upon the model chosen. Experiments which would provide further information on the potentials for HF systems are suggested. The potentials for the rare gas-HF systems are considerably more anisotropic than for the corresponding rare gas-HCl systems. The contributions of induction and dispersion forces to the potential anisotropy are discussed and both are found to be significant. It seems likely that the attractive forces can be adequately described in terms of induction and dispersion forces alone, without the need to invoke incipient chemical bonding.