Hydrogen atoms look into a helium mirror

Abstract

In a recent series of elegant experiments a group at the University of Amsterdam have bounced cold (T⩽400 mK) hydrogen atoms off a spherical mirror coated with superfluid helium-4 and used this to study the interactions between the H atoms and the 4He surface. In doing so J Berkhout and colleagues have approached the limit of ultra-low energy surface scattering described by 'quantum reflection' (1989 Phys. Rev. Lett. 63 1689).