Abstract

We studied the low-energy limit of atomsurface scattering and the phenomenon of quantum reflection by using hydrogen atoms and the surface of liquid helium. Measuring the specular reflectivity of a liquid-helium-covered hemispheric mirror for a beam of hydrogen atoms we obtained information on elastic and inelastic scattering phenomena. At 100 mK, reflectivities larger than 90% were achieved; this can be used to demonstrate atomic beam focusing. Approximately three-fourths of the atoms escaping from a small orifice in a cell were reflected back into the cell. The dominant inelastic processes at work here are surface absorption and direct inelastic scattering over small angles under excitation of surface ripplons (quantized capillary waves). Helium-covered surfaces maybe useful for atomic-beam manipulation of atomic hydrogen.

© 1990 Optical Society of America