Coherent reflection of He atom beams from rough surfaces at near-grazing incidence

TL;DR

This study demonstrates coherent reflection of thermal helium atom beams from rough surfaces at grazing incidence, revealing quantum reflection effects and the influence of surface roughness and material properties on reflection probabilities.

Contribution

It provides new insights into quantum and classical reflection mechanisms of atom beams at rough surfaces under grazing incidence conditions.

Findings

Reflection probability depends on the normal wave-vector component for small $k_z$

Quantum reflection occurs at the attractive Casimir-van der Waals potential branch

Material-specific $k_x$ dependence arises from surface roughness effects

Abstract

We here report coherent reflection of thermal He atom beams from various microscopically rough surfaces at grazing incidence. For a sufficiently small normal component $k_z$ of the incident wave-vector of the atom the reflection probability is found to be a function of $k_z$ only. This behavior is explained by quantum-reflection at the attractive branch of the Casimir-van der Waals interaction potential. For larger values of $k_z$ the overall reflection probability decreases rapidly and is found to also depend on the parallel component $k_x$ of the wave-vector. The material specific $k_x$ dependence for this classical reflection at the repulsive branch of the potential is explained qualitatively in terms of the averaging-out of the surface roughness under grazing incidence conditions.