Desorption kinetics of Li atoms from LiF under electron bombardment

Measurements on electron stimulated desorption (ESD) of Li atoms in the electronical ground state (Li 0 ) from air-cleaved LiF(100) surfaces have been performed. The electron energy was varied between 50 and 450 eV. After electron bombardment was stopped, a prompt decrease of the Li 0 signal followed by a delayed emission of Li 0 was observed. In the temperature range from 620 to 720 K the delayed emission of Li 0 shows a behavior, which could not be explained by diffusion of F centers to the surface only. Delayed emission of Li 0 up to minutes was observed and we therefore suggest, that energy must be stored in the bulk through the formation of F center aggregates in order to explain the experimentally observed behavior of the delayed emission. A system of rate equations has been developed, which describes the kinetics of formation and decay of F center aggregates.