Sticking coefficient at ultralow energy: Quantum reflection

Some sixty years ago, Lennard-Jones and Devonshire predicted that the low energy behavior of the sticking coefficient is s ∝ √E, which vanishes as the energy approaches zero. This behavior is called quantum reflection. The prediction differs from the classical limit s = 1, because the wave function of the impinging particle is reflected at large distance from the surface. The present article explains why and when the prediction is valid, when it is not valid, and the nature of the experimental confirmation to date. Other related predictions are discussed.