Paper SS2-FrM9
HD Scattering on Cu (001): Rotationally Mediated Bound State Resonances and Evidence for Interaction of the Bound States with the Surface Phonons
Seeded HD molecular beams have been used to study the laterally averaged HD - Cu (001) physisorption potential by measurements of rotationally mediated bound state resonances (BSR). The physisorption well depth of 30.5 meV was confirmed using a Le Roy plot by combining our HD data with existing H@sub 2@ and D@sub 2@ data. The positions of all rotationally mediated bound state resonance energies are determined well by the results of calculations using different potentials. BSR energies from isotropic potential calculations are considerably higher than the experimentally determined energies, as well as those of the values calculated with an anisotropic potential. So the anisotropic part of the potential cannot be neglected. Calculations predict lower energy for m@sub J@ = 0, indicating that the molecule prefers to have its molecular axis perpendicular to the surface (cartwheel rotation). A considerable shift of the bound state levels in the presence of an adsorbate (chemisorbed hydrogen) is also observed. Resonance energies do not change with the surface temperature. The Debye-Waller analysis of the intensities and the widths of the resonance features show a coupling between the resonant states and surface phonons. The strongest coupling is for the states lower in the potential well.