Light-induced diffusion and desorption of alkali metals in a siloxane film: Theory and experiment

The light-induced desorption and diffusion of alkali-metal atoms in organic films are interesting fields of investigation. An impressive demonstration is given by the recently observed light-induced atomic desorption (LIAD) e ffect, where a huge alkali-metal atom desorption from siloxane films, previ ously exposed to atomic vapors, is induced by weak and nonresonant light. I n this paper, experimental data and a one-dimensional theoretical model of the effect are presented. The model gives a good description of the vapor d ensity dynamics by taking into account both the atomic diffusion inside the coating and the surface desorption. General equations are reported and dis cussed within the limits of experimental interest. The potential barrier at the vapor-surface interface and the activation energy for Rb in (poly)dime thylsiloxane have been determined. [S1050-2947(99)01512-7].