VANDERBILT UNIV NASHVILLE TN DEPT OF PHYSICS AND ASTRONOMY
The mechanism leading to photon-stimulated desorption PSD of excited atoms from the surfaces of alkali halides has been a subject of controversy since it was first discussed a decade ago. We have recently carried out a systematic experimental study of PSD from alkali halides under both valence-band and core-level excitation. Our data demonstrate that the desorption yields for excited alkali atoms track the excitonic optical response of these crystals even at photon energies below the bulk band gap. Secondary electron measurements, taken simultaneously, implicate the formation of excess metal in the time and dose dependence of PSD yields. These results suggest a unified picture of PSD in which the ion motion initiating desorption is pictured as the decay of a localized, highly deformed vibrational mode of the crystal. Plausible mechanisms for creation of the excited atomic state include relaxation of excited F-centers and resonant neutralization into the excited state on metallic microclusters.
This article is from 'Organization of the Optical Society of America Photonic Science Topical Meeting Series. Volume 3. The Microphysics of Surfaces: Beam-Induced Processes. Held in Santa Fe, New Mexico on 11-13 Feb 1991,' AD-A254 135,p157-160.