Detection of high-energy adsorbate vibrational modes by atom-surface scattering

Abstract

It is suggested that high-frequency vibrational modes of surface adsorbates can produce very characteristic signature features in the observable inelastic intensity in experiments using atomic beams as scattering probes. These features consist of peaks in the inelastic background, due to multiquantum excitation of the high-energy vibrational modes, and these peaks are significantly broadened and shifted in the direction of energy loss by the multiphonon scattering arising from the substrate and other low-energy adsorbate modes. Calculations for the scattering of rare gases from several types of adsorbate indicate that, by selecting the probe projectile species and tuning the incident energy and incident beam angle, selected high-energy modes can be excited, and the method can be used to accurately measure the vibrational frequencies and polarizations of these modes.