Rotationally Mediated Selective Adsorption as a Probe of Isotropic and Anisotropic Molecule—Surface Interaction Potentials: HD(J)/Ag(111)

Abstract

Rotationally mediated selective adsorption scattering resonances are used to make an experimental and theoretical study of the laterally averaged interaction potential between HD and a weakly corrugated system, Ag(111). The experimentally observed resonances determine the vibrational levels of the HD/Ag(111) physisorption potential as a function of bound rotational state. These vibrational levels show J‐dependent shifts due to the orientational anisotropy of the potential. Exact quantum scattering calculations using a full laterally averaged potential of the form have been carried out to obtain rotationally inelastic transition probabilities. Experimental and theoretical resonance energies are compared for two forms of v_o(z), a Morse and a variable exponent potential, as a function of β, and are found to be very close to the first‐order perturbed energies of a free rotor in bound states of v_o(z). Both potential forms give equally good fits to the data, yielding an optimum value of the asymmetry parameter, β ≈ — 0.05. The determination of β is relatively insensitive to small changes in the v_o(z) well depth.