LOW-ENERGY-ELECTRON TRANSMISSION IN SOLID KRYPTON AND XENON FILMS

Low-energy-electron-transmission (LEET) spectra of krypton and xenon f ilms deposited on a platinum substrate exhibit a peak at an energy som ewhat below the center of the respective GAMMA3/2n = 1 exciton band. T he peaks were systematically studied as a function of the film thickne ss. They were attributed to a process in which an electron loses a lar ge part of its energy by creating a GAMMA3/2n = 1 exciton and conseque ntly ends up in the conduction band of the rare-gas solid beneath the vacuum level. A simple model was formulated, taking into account the s hape of the optical-absorption band and the image forces at the sample boundaries. Fitting the position, width, and height of the experiment ally observed peaks in the thickest films (approximately 100 monolayer s or more) lead to the determination of the conduction-band energy V0 and exciton band parameters in good agreement with the results of phot oelectric and optical-absorption experiments. However, for thinner fil ms the LEET peaks were much broader than predicted by theory. The poss ible reasons for this behavior are discussed in brief.