Excitonic transitions of ordered layers of Xe on ag(111) and Al(111): A low-energy EELS study

Abstract

We present the results of low-energy electron energy loss spectroscopy (EELS) studies of the lower excitonic transitions of Xe thin films on single crystal Ag(111) and Al(111) surfaces. We find that the spectra of cold (≈20 K) deposited, disordered Xe films can be interpreted in terms of broadened atomic-like transitions. However, the spectra of ordered Xe layers. obtained upon annealing, show extra transitions with no optical counterparts. These observations are explained in terms of significant dispersion and lifting of the degeneracy of levels in ordered layers of Xe. Low-energy EELS allows transitions to the split excitonic levels involving large momentum transfer. © 1984.