A flash desorption technique is used to show that helium atoms desorbing from a hot surface are emitted within a narrow cone about the normal direction. The emission angle and the energy of the atoms are highly correlated, which results in a "rainbow" in the desorption spectrum. These effects are discussed in terms of single-particle conservation conditions for energy and momentum transfer between phonons and atoms.

• Received 19 February 1982

DOI:https://doi.org/10.1103/PhysRevLett.48.1737