Interaction of Rare Gases and H₂with Surfaces of Magnesium Oxide and Other Insulators

We propose a new model potential to describe the interaction between rare-gas atoms and H₂with surfaces of insulators. The potential consists of a repulsive part calculated by using the effective medium theory and an attractive part due to dispersion forces. We find that our potential gives shallower well depths than given by experiments. However, if we let C₆range within reasonable bounds, our potential fits the corrugation of the surface and the bound-state energies very well. We discuss in particular the He/MgO case, for which contradictory experimental results exist. Our model supports the recent data of Frankl'2 group, which predicts a shallower well depth than previously measured. We also comment on which parameters of the potentials should be known more accurately in order to bring calculations and experimental data to a closer agreement.