Specular Reflection of Very Slow Metastable Neon Atoms from a Solid Surface

An ultracold narrow atomic beam of metastable neon in the 1s₃[\(2s\)⁵3p:¹P₀] state is used to study specular reflection of atoms from a solid surface at extremely slow incident velocity. The reflectivity on a silicon (1,0,0) surface and a BK7 glass surface is measured at the normal incident velocity between 1 mm/s and 3 cm/s. The reflectivity above 30% is observed at about 1 mm/s. The observed velocity dependence is explained semiquantitatively by the quantum reflection that is caused by the attractive Casimir-van der Waals potential of the atom-surface interaction.