Refraction of Fast Ne Atoms in the Attractive Well of a LiF(001) Surface

Abstract

Ne atoms with energies of ≤3 keV are diffracted under grazing angles of incidence from a LiF(001) surface. For a small momentum component of the incident beam perpendicular to the surface, we observe an increase in the elastic rainbow angle together with a broadening of the inelastic scattering profile. We interpret these two effects as the refraction of the atomic wave in the attractive part of the surface potential. We use a fast, rigorous dynamical diffraction calculation to find a projectile–surface potential model that enables a quantitative reproduction of the experimental data for ≤10 diffraction orders. This allows us to extract an attractive potential well depth of 10.4 meV. Our results set a benchmark for more refined surface potential models that include the weak van der Waals region, a long-standing challenge in the study of atom–surface interactions.

Grazing incidence fast atom diffraction, similarities and differences with thermal energy atom scattering (TEAS)

“…The time step also should be adapted to smaller values. Using the ASCA, only the slow motion in the (y,z) plane has to be considered and wave packet propagation 11,[31][32][33] or close coupling approaches 34,35 have been successfully applied. The accuracy of the axial channeling approximation was investigated in detail by extensive 3D calculations compared with the simplified 2D ASCA.…”

“…In ref. 35, diffraction data from neon displayed in Fig. 7 and 8 were compared with a recent ab initio calculation of the PEL by Miraglia and Gravielle 79 who kindly accepted to provide a compact description of their results in the form of effective binary interaction potentials.…”

“…79 optimized to the data by a new close coupling code 106 providing the first quantitative agreement. 35 vibrational transition can be calculated exactly as p e = |hc|e idkz |ci| 2 which, for an atom initially in the vibrational ground state is proportional to p e p e ÀEr/h oD (eqn (3)). This probability is significant only when the recoil energy is less than a vibrational energy quantum 21 and can be identified as the Mössbauer-Lamb-Dicke probability for recoil-less photon emission characteristic of a trapped atom, for instance in an optical lattice.…”

“…Experimentally, a combined GIFAD and HAS study of a thin overlayer, for instance of graphene, 100 would probably help in the identification of specific vibration modes and allow significant progress. Regarding elastic diffraction, the recent progress 35 should allow for the implementation of a crystallographic software starting with a qualitative adjustment of surface atoms coordinates and effective binary interaction potentials by the HCW model and then final quantitative optimization by quantum scattering programs.…”

Atom-surface van der Waals potentials of topological insulators and semimetals from scattering measurements

“…The effect of 85 the attractive part of the potential onto the incident He atom can be seen as an analogy to refraction for classical scattering from an isolated target. Since only the z-component is important, refraction can also be made visible in the case of fast Ne atoms, if angles close to grazing incidence are used 24 .…”