Integer versus noninteger valence properties revealed by a comparative photoemission study of NaxWO3 and ReO3

Fano-type resonances in the 5d conduction-band intensity spectra have been observed at the 5p12 and 5p32 photoabsorption thresholds for NaxWO3 (0.4<x<0.85), ReO3, WO2, and W. The NaxWO3 tungsten-bronze spectra exhibit a characteristic double resonance structure different from the simple resonance peaks measured for ReO3, WO2, and W. These results could be related to a mixed-valence character of the metallic bronzes in the final state of the photoemission process. The complex structure of the photoelectron corelevel 4f spectra for NaxWO3 and ReO3 is discussed on the basis of these new findings. © 1983 The American Physical Society.