A simple theoretical model for the van der Waals potential at intermediate distances. II. Anisotropic potentials of He–H2 and Ne–H2

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Abstract
A simple model proposed in an earlier paper [J. Chem. Phys. 66, 1496 (1977)] is applied to the prediction of the radial V0(R) and anisotropic parts v2(R) of the van der Waals potentials, V (R,γ) =v0(R)+v2(R) P2 (cosγ), where R is the distance between centers of mass and γ is the angle between R and the molecular axis, for He–H2 and Ne–H2. All the parameters used in the model are derived either from ab initio SCF data on the repulsive potential calculated by Hariharan and Kutzelnigg or from perturbation calculations of Meyer of the long range dispersion terms and their angular dependence. The predicted v0 and v2 radial dependences for He–H2 are compared with several of the latest ab initio CI‐type calculations. For Ne–H2, for which ab initio potentials are not available in the potential well region the results are compared with the most reliable experiments. In addition the predicted potentials are used to calculate the orientation dependence of total integral cross sections for direct comparison with measurements by Reuss and co‐workers for both systems. In all cases excellent agreement within a few percent is obtained. These results demonstrate for the first time that the model also describes the repulsive potential up to energies of about 10 meV. The possible physical implications of the model potential are briefly discussed.