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

C A Ríos Rubiano,G A Bocan,J I Juaristi,M S Gravielle

doi:10.1103/physreva.89.032706

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 $[1\overline{1}2]$ and $[1\overline{1}0]$ 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 $[1\overline{1}2]$ 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.

Highlights

Since the unexpected observation of grazing incidence diffraction of fast atoms (GIFAD) on crystal surfaces [1,2], extensive research, both experimental and theoretical, has been devoted to the subject [3,4,5,6,7,8,9,10,11]
In the figure we show theoretical results corresponding to a monoenergetic incident beam, together with values obtained by including the experimental energy spread by means of a convolution [40]
We have studied the energy lost by helium atoms after grazingly colliding with a silver surface along low-indexed crystallographic directions

Summary

Introduction

Since the unexpected observation of grazing incidence diffraction of fast atoms (GIFAD) on crystal surfaces [1,2], extensive research, both experimental and theoretical, has been devoted to the subject [3,4,5,6,7,8,9,10,11]. Meaningful energy losses were recently reported for grazing scattering of H atoms from a LiF(001) surface [12,17], where inelastic electronic processes were found to produce a diffuse background in the experimental GIFAD distributions. The aim of this work is to study the energy lost by swift He atoms after grazing impinging on a Ag(110) surface along lowindexed crystallographic directions, under the same conditions for which diffraction has been observed [7]. This collision system corresponds to the first and simplest metallic case for which experimental GIFAD distributions were reported in conjunction with measurable energy losses [7]

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Results

Conclusion