Inelastic Phonon Scattering of Helium atoms from the reconstructed Au(111) surface

We present inelastic atom-surface phonon scattering time-of-flight spectra for the reconstructed Au(111) surface. The shapes of the spectra are compared with calculated reflection coefficients based on a simplified lattice dynamical model for the reconstructed surface. The force constants were determined from a best fit of the surface phonon dispersion curves and the lateral atom-atom interactions in the surface layer were found to be 30% of the bulk value. The theoretical spectra reproduce the overall lineshape of the experimental spectra and reveal additional features which can be attributed to the reconstruction of the surface layer with respect to the substrate.