Abstract

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 [1]. We have recently carried out a systematic experimental study of PSD from alkali halides under both valence-band [2] and core-level [3] 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.

© 1991 Optical Society of America