Energy-loss contribution to grazing scattering of fast He atoms from a silver surface

Abstract

The energy lost by helium atoms axially scattered from a Ag(110) surface is studied in order to investigate the influence of dissipative processes on fast atom diffraction spectra. In this work inelastic projectile distributions are evaluated within a semiclassical formalism that includes dissipative effects due to electron-hole excitations through a friction force. For incidence along the [112] and [110] directions the model predicts the presence of multiple peaks in the energy-loss spectrum for a given impact energy. But these structures are completely washed out when the experimental dispersion of the incident beam is taken into account, giving rise to a smooth energy-loss distribution. Simulations including the experimental energy spread are in fairly good agreement with available experimental data for the [112] channel. In addition, our results suggest that inelastic processes produce an almost constant background in the transverse momentum distribution, except in the extremes of the momentum range where classical rainbow maxima appear. By adding elastic and inelastic contributions, experimental diffraction patterns are well reproduced.

Trajectory-dependent energy loss for swift He atoms axially scattered off a silver surface

“…In this work we extend a previous study [32] to investigate the energy lost by 3 He atoms grazingly colliding with Ag(110) along the [1 10], [1 12] and [001] channels. Impact energies E i ranging from 0.5 keV to 2 keV and perpendicular energies E i⊥ = E i sin 2 θ i varying from 0.15 eV to 0.87 eV are considered, θ i being the incidence angle measured with respect to the surface plane.…”

Stereodynamics effects in grazing-incidence fast-molecule diffraction

“…All these tools are based on the Born-Oppenheimer approximation (BOA), where the PESs can be computed using pairwise-like analytical functions 18,19,30,39,[45][46][47][48] or density functional theory (DFT). 21,25,26,33,[49][50][51][52][53][54][55] PESs computed at multiconfiguration self-consistent field level, considering a cluster model, have also been used. 1,17 To perform the dynamics calculations, several approaches have been adopted, from classical 49,51,52 to quantum 1,12,17,26,30,47,55 methods, as well as semiclassical 28,36,41,56 and semi-quantum 18,21,25,50,53,[57][58][59] methods.…”

Single- and double-slit collimating effects on fast-atom diffraction spectra

“…In the last time grazing-incidence fast atom diffraction (GIFAD or FAD) [1,2] has emerged as a powerful surface analysis technique that allows one to inspect ordered surfaces, providing detailed information on their morphological and electronic characteristics [3][4][5]. The extreme sensitivity of FAD patterns to the projectile-surface interaction relies on the preservation of quantum coherence [6][7][8][9], and in this aspect the collimating conditions of the incident beam play an important role. In particular, recent experimental [10] and theoretical [11] works have shown that FAD patterns are strongly affected by the width of the collimating aperture, which determines that two different mechanisms -Bragg diffraction or supernumerary rainbows -can be alternatively observed.…”