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

Low-energy-electron-transmission (LEET) spectra of krypton and xenon films deposited on a platinum substrate exhibit a peak at an energy somewhat below the center of the respective GAMMA3/2n = 1 exciton band. The peaks were systematically studied as a function of the film thickness. They were attributed to a process in which an electron loses a large part of its energy by creating a GAMMA3/2n = 1 exciton and consequently ends up in the conduction band of the rare-gas solid beneath the vacuum level. A simple model was formulated, taking into account the shape of the optical-absorption band and the image forces at the sample boundaries. Fitting the position, width, and height of the experimentally observed peaks in the thickest films (approximately 100 monolayers or more) lead to the determination of the conduction-band energy V0 and exciton band parameters in good agreement with the results of photoelectric and optical-absorption experiments. However, for thinner films the LEET peaks were much broader than predicted by theory. The possible reasons for this behavior are discussed in brief.