Spectroscopically observed valence mixing in SmS and related compounds

Photoemission spectra for semiconducting SmS and metallic Sm0.5Y0.5S give evidence of strong configuration interaction of localized states near the Fermi level involved in semiconductor-to-metal phase transitions and in unusual transport and magnetic properties. An analysis of the observed multiplet structure in photoemission spectra for semiconducting SmS shows a localized state of a mixed f6+f5d character. © 1974 The American Physical Society.