Investigation of the spatially anisotropic component of the laterally averaged molecular hydrogen/Ag(111) physisorption potential

A detailed investigation of the spatially anisotropic component of the laterally averaged molecular hydrogen/Ag(111) physisorption potential is presented. Experimentally derived rotationally inelastic transition probabilities for H2, D2, and HD, taken as a function of collision energy, are compared with those resulting from close-coupled quantum scattering calculations. These calculations utilize exponential-3 and variable exponent parametrizations of the laterally averaged isotropic potential which reproduce the experimental bound state resonance spectra for p-H2 and o-D2 on Ag(111). Complementary information is obtained by analyzing the magnetic sublevel splittings for physisorbed J=1 n-H2, using diffractive selective adsorption resonance energies calculated with first order perturbation theory. Theoretical predictions for HD/Ag(111) rotationally mediated selective adsorption resonances are also compared with previously reported experimental results, which show well resolved J-dependent energy shifts resulting in part from the orientational anisotropy of the potential. The results obtained in this study indicate that both the attractive and repulsive parts of the anisotropic potential exhibit only a weak orientation dependence, in agreement with recent theoretical predictions for this system.