Core exciton in sodium halides studied by photoelectron spectroscopy.

Abstract

The constant-initial-state (CIS) spectrum with the initial state at the peak of the valence band, and the constant-final-state spectrum with the final state at the kinetic energy of the Auger electron, were measured at photon energies near the Na 2p core exciton excitation in NaCl and NaBr with two different incident angles of the photon beam against the sample surface. Two peaks were observed in the CIS spectra. The higher-energy peak, which appears at the same photon energy as that of the dominant exciton peak in the absorption spectrum, is attributed to the decay of the bulk core exciton. The lower-energy peak, whose intensity and energy position strongly depend on the polarization of photons incident on the sample surface, is ascribed to the decay of the surface core exciton.