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

Low-intensity ${(10\mathrm{}}^{\mathrm{-}5}$–${10}^{\mathrm{-}2}$ watts/${\mathrm{cm}}^2$) IR radiation at 9–15 μm 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.