Ne atom scattering from Ir(111) under nearly classical conditions

•Experimental data is compared to theoretical calculations for Ne scattering from Ni(111) under classical scattering conditions.•Ne can lose or gain energy through multiphonon scattering events which is well explained by a classical theory of scattering.•The peaks observed in the energy resolved spectra can possibly be mistaken for single-phonon features.•It is shown how false single-phonon dispersion curves can be explained as multiphonon features. [Display omitted] Measurements of Ne atom scattering from a clean and ordered Ir(111) surface are shown under conditions in which the scattering is nearly classical. The only quantum mechanical manifestation is a small elastic specular diffraction intensity. The energy-resolved intensity spectra exhibit only a single broad peak attributed to multiple phonon excitations. The multiphonon peak is well explained by classical scattering theory. It is shown that the multiphonon peak can mimic the behavior of a single-phonon dispersion curve, however, measurements at different incident energies can be used to identify this false dispersion curve.