Quantum Scattering of Fast Atoms and Molecules on Surfaces

Abstract

We present evidence for the diffraction of light keV atoms and molecules grazingly scattered on LiF(001) and NaCl(001) surfaces. At such energies, the de Broglie wavelength is 2 orders of magnitude smaller that the mean thermal atomic displacement in the crystal. Thus, no coherent scattering was expected and interaction of keV atoms with surfaces is routinely treated with classical mechanics. We show here that well-defined diffraction patterns can be observed indicating that, for grazing scattering, the pertinent wavelength is that associated with the slow motion perpendicular to the surface. The experimental data are well reproduced by an ab initio calculation.

Diffraction of helium on MgO(100) surface calculated from first-principles

“…The scattering of He atom beams on crystal surfaces has the potential to be an important technique for determining the atomistic structure and dynamics of surfaces. [1][2][3][4][5][6] The He beam scatters from only the outermost surface layers unlike X-ray diffraction and it neither damages or charges the surface unlike electron diffraction and microscopy. During the last two decades its usefulness has been demonstrated in the determination of numerous surface structures.…”

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

“…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. In particular, the study of the mechanisms that contribute to the coherence or decoherence of the scattered particles is still in its infancy.…”

Open quantum system approach in multiple atomic collisions in solids and gases

“…Because of the very different parallel and perpendicular momenta, the wave nature of the wavepacket becomes important even for beam energies of several keV permitting observation of diffraction patterns [19,20]. Kiloelectronvolt beams, however, undergo inelastic collisions with the thermally excited lattice providing a source of decoherence that should influence the contrast of the diffraction patterns.…”