X-ray photoemission studies of the alkali halides

High resolution x-ray photoemission spectra of the alkali halides LiF, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, and KI are reported. The valence-band spectra are compared with previous spectra of group-IV,-III-V, and -II-VI crystals. It is shown that features of the spectra evolve systematically in proceeding from the group-IV elements to the I-VII crystals. Analysis of this evolution leads to the interpretation of the structure of the outermost halogen $p$ band in the less ionic cases as being due to band effects rather than spin-orbit splitting. The outermost-core-level binding energies are tabulated. Intrinsic and extrinsic satellite structure associated with the core levels is discussed.