The Characteristic Electron Energy Loss Spectra of Some Alkali Halides

Abstract

The characteristic electron energy loss spectra of the alkali halides LiF, LiCl, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbCl, CsBr and CsI, were measured using primary energies of 800 eV and 1500 eV. In each spectrum a peak due to the excitation of the valence electron plasma oscillation is observed. There is good agreement between this energy loss and the plasma energy hπp, calculated assuming that the valence electrons are able to participate in such oscillations. In some of the spectra a loss peak at energy approximately hπp/√2 is observed, which also appear to be due to the excitation of a longitudinal plasma oscillation, although these are not identified with present theory.