Fano-type resonances in the $5d$ conduction-band intensity spectra have been observed at the $5p_{\frac{1}{2}}$ and $5p_{\frac{3}{2}}$ photoabsorption thresholds for ${\mathrm{Na}}_x\mathrm{W}{\mathrm{O}}_3$ ($0.4<x<\mathrm{}0.85\mathrm{}$), Re${\mathrm{O}}_3$, W${\mathrm{O}}_2$, and W. The ${\mathrm{Na}}_x\mathrm{W}{\mathrm{O}}_3$ tungsten-bronze spectra exhibit a characteristic double resonance structure different from the simple resonance peaks measured for Re${\mathrm{O}}_3$, W${\mathrm{O}}_2$, 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 ${\mathrm{Na}}_x\mathrm{W}{\mathrm{O}}_3$ and Re${\mathrm{O}}_3$ is discussed on the basis of these new findings.

• Received 26 July 1982

DOI:https://doi.org/10.1103/PhysRevB.27.6370