Comparison of inelastic scattering of Ne and He on Ag(111)

Abstract Time-of-flight measurements of He beams and of high resolution Ne beams on an Ag(111) surface along the 〈11 2 〉 direction are reported. In order to compare the scattering probabilities of He and Ne, the same crystal and similar experimental conditions like surface temperature and angular resolution are used. Both for Ne and He beams with kinetic energies of ∼ 20 meV single phonon processes dominate at least for small momentum transfers. The features in the time-of-flight spectra can be attributed to the Rayleigh mode, the quasi-longitudinal surface resonance and, in the case of Ne, to scattering processes with zero momentum transfer. The relative intensities of these modes are discussed in terms of the lateral momentum transfer. For Ne the intensity of inelastic scattering processes normalized to the specular intensity is larger than for He.