CONSTRUCTIVE INTERFERENCE EFFECTS IN ENERGY-LOSS SPECTRA OF ENERGETIC NOBLE-GAS IONS AND ATOMS INCIDENT AT GLANCING INCIDENCE TO METAL-SURFACES

Scattering Of energetic noble gas ions and atoms at grazing incidence from smooth (111) surfaces of metals (Cu, Al) produces energy loss distributions with a no-loss contribution of low intensity (small Debye-Waller factor) and a broad inelastic sideband. At keV beam energies, this sideband is typically peaked at a few to several tens of eV below the no-loss contribution. We propose that electronic excitations in the metal are responsible for dissipation of the scattered particle kinetic energy, and argue that the observed magnitude can only be explained by assuming a fluctuating effective charge or dipole on the moving particle. Constructive interference between successive fluctuation steps gives rise to a high probability of translational energy loss and leads to the experimentally observed shape of the loss spectra.