Diffraction of fast atoms and molecules from surfaces

TL;DR

This paper develops a quantum mechanical and classical theory for the diffraction of fast atoms and molecules from surfaces, explaining experimental observations of coherent and incoherent scattering regimes.

Contribution

It introduces a comprehensive model describing surface scattering of fast atoms, including quantum, classical, and intermediate regimes, with novel insights into Debye-Waller factor behavior.

Findings

Quantum limit shows coherent diffraction peaks with large Debye-Waller factors.

Classical limit describes incoherent scattering at high energies and temperatures.

Intermediate regime features broadened diffraction peaks unaffected by simple Debye-Waller models.

Abstract

Prompted by recent experimental developments, a theory of surface scattering of fast atoms at grazing incidence is developed. The theory gives rise to a quantum mechanical limit for ordered surfaces that describes coherent diffraction peaks whose thermal attenuation is governed by a Debye-Waller factor, however, this Debye-Waller factor has values much larger than would be calculated using simple models. A classical limit for incoherent scattering is obtained for high energies and temperatures. Between these limiting classical and quantum cases is another regime in which diffraction features appear that are broadened by the motion in the fast direction of the scattered beam but whose intensity is not governed by a Debye-Waller factor. All of these limits appear to be accessible within the range of currently available experimental conditions.