Ab initiopotential for the He-Ag(110) interaction investigated using grazing-incidence fast-atom diffraction

Abstract

Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test an ab initio potential model derived from accurate density-functional theory (DFT) calculations. The scattering process is described by means of the surface eikonal approximation, which is a distorted-wave method that includes the quantum interference between contributions coming from different projectile paths, taking into account the complete corrugation of the three-dimensional projectile-surface potential. A fairly good agreement between the theoretical and experimental momentum distributions is found for incidence along different low-indexed crystallographic directions. This agreement is indicative of the quality of the DFT potential. The effective corrugation of the interaction potential across the incidence channel is also investigated.

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

“…In a previous paper [18], GIFAD patterns for He atoms scattered off Ag(110) were investigated considering different energies associated with the motion normal to the surface plane. The calculations were performed to represent the elastic * Author to whom correspondence should be addressed: msilvia@iafe.uba.ar regime, neglecting inelastic contributions and associated decoherence.…”

Semiquantum approach for fast atom diffraction: Solving the rainbow divergence

“…In spite of the successful performance of the SE approach for the simulation of FAD patterns, a weakness of the theory is its deficient description of the rainbow effect, which affects the intensity of the outermost diffraction maxima when these maxima are close to the classical rainbow angles [22], i.e. the extreme deflection angles of the classical projectile distribution .…”

Influence of beam collimation on fast-atom diffraction studied via a semiquantum approach

“…This strategy incorporates an approximate description of classically forbidden transitions on the dark side of rainbow angles, making it possible to avoid the classical rainbow divergence present in previous semi-classical models for FAD, like the Surface-Eikonal (SE) approach [19,20]. Such a weakness of the SE method affects the intensity of the outermost diffraction maxima when these maxima are close to the classical rainbow angles [11], i.e. the extreme deflection angles of the classical projectile distribution.…”

“…In recent years the FAD method was successfully applied to very different kinds of materials, ranging from insulators [4][5][6] to semiconductors [7,8] and metals [9][10][11], as well as structured films [12] and molecules [13] adsorbed on surfaces. However, in spite of the extensive experimental and theoretical work devoted to the research of FAD since its first experimental observation [4,5], the complete understanding of the underlying quantum processes is far from being achieved.…”