Infrared-induced single-phonon desorption of HD from LiF (100)

Abstract

Low-intensity ${(10}^{\mathrm{\ensuremath{-}}5}$--${10}^{\mathrm{\ensuremath{-}}2}$ watts/${\mathrm{cm}}^{2}$) IR radiation at 9--15 \ensuremath{\mu}m desorbs HD from 1.5--4.2-K LiF (100) at a rate (maximum 0.001 monolayer/s) proportional to the light intensity. This process is independent of temperature below 4.2 K, the velocity distribution is approximated by a temperature of 21 K, and the desorption efficiency increases with increasing wavelength. Desorption is attributed to single phonons created in a cascade following optical absorption. Thermal desorption is excluded as a possible mechanism except at high surface temperatures and coverages.