Experimental and theoretical investigation of the multiple phonon excitation of monolayer film modes with helium atom scattering: KrÕPt„111..

Energy resolved helium atom scattering results for the multiple excitation of the perpendicular vibrations ~S modes! of a krypton monolayer adsorbed on Pt~111! are presented for a wide range of incident angles. These measurements, which were obtained for incident helium atom energies much greater than the fundamental S-mode energy, are modeled within a general multiphonon scattering theory using a simple scattering form factor for a repulsive potential. The good agreement between experiment and theory indicates that the details of the He-surface interaction potential are relatively unimportant for incident energies much higher than the vibrational energy.