Information on Adsorbate Positions from Low-Energy Recoil Scattering: Adsorption of Hydrogen on Pt

Low-energy (10-keV) recoil scattering is proposed as a tool for measurement of adsorbate positions on monocrystalline surfaces. This technique, which makes use of high-energy-recoil adsorbate atoms (energy 1 keV), supplies real-space structure information. Its potentialities are illustrated in a study of the adsorption system H on (111) sites of Pt. By exploiting surface channeling of incident 10-keV Ne ions on vicinal Pt surfaces we show unambiguously that H occupies fcc-type adsorption sites on Pt (111) terraces.