Physisorption Interaction of Hydrogen With Noble-Metal Surfaces: a New H sub 2 --Cu Potential

Using molecular beams of hydrogen and deuterium with incident energies and angles in the ranges 5-50 meV and 40-80 deg , diffractive selective adsorption scattering resonances were measured from a Cu(100) surface kept at 80K. From the dispersion relations--resonance energy vs. incident angle--the resonances have been unambiguously identified, and the appropriate bound-state level energies have been determined. These data have been analyzed and a level assignment arrived at, that is compatible with a single gas-surface potential curve for H and D. A well depth of 30.9 meV was found, which is substantially larger than the commonly accepted value approx 22 meV for the H sub 2 --Cu system. The data strikingly resembled those reported for the H sub 2 --Ag system and these observations are discussed in relation to theoretical predictions. 20 ref.--AA