SURFACE CORE EXCITON IN LICL STUDIED BY PHOTOELECTRON-SPECTROSCOPY

The surface core exciton as well as the bulk core exciton were observed by means of photoelectron spectroscopy for the (001) surface of a LiCl single crystal by using polarized light from a storage ring. Constant-initial-state spectra with the initial state at the valence band were measured with various angles of incidence of the exciting light for photoemission. Spectra show two peaks around the excitation photon energy of the Li 1s core exciton. The intensity of the lower-energy peak relative to that of the higher-energy one, which has been attributed to the bulk core exciton, increases drastically with the increase of the angle of incidence. The origin of the lower-energy peak is attributed to the decay of the surface core exciton.