Abstract
Inelastic helium scattering has been used to investigate the influence of oxygen adsorbate on the Pt(111) surface phonons. Oxygen adsorbed on a p(2×2) superstructure on Pt(111) was found to induce a clear anisotropy in the Rayleigh phonon dispersion relation. The increased anisotropy is explained by oxygen adsorption at the ‘‘hcp sites’’ of the Pt(111) surface.