Vacuum-ultraviolet spectra and band structure of ${\mathrm{BaPb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Bi}}_{\mathrm{x}}$${\mathrm{O}}_3$

The electronic structure of ${\mathrm{BaPb}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Bi}}_{\mathrm{x}}$ ${\mathrm{O}}_3$ is investigated by using vacuum-ultraviolet reflectivity spectra in the energy range 2–35 eV. The origins of the observed optical transitions are discussed together with the results of ultraviolet photoelectron and electron-energy-loss spectroscopies. Overall features of the observed excitations can be well explained by the calculated band structure, whereas the relatively-low-energy spectrum up to 8 eV shows features distinct from the band-calculation results because of the effect of possible charge-density-wave formation.