Partial spectral weights of disordered ${\mathrm{Cu}}_{\mathit{x}}$${\mathrm{Pd}}_{1\mathrm{-}\mathit{x}}$ alloys including the photoemission matrix-element effect

The valence-band photoemission spectra of disordered ${\mathrm{Cu}}_{\mathit{x}}$ ${\mathrm{Pd}}_{1\mathrm{-}\mathit{x}}$ alloys are measured with synchrotron radiation in the soft-x-ray regime. Taking advantage of the Cooper-minimum phenomenon of the Pd 4d photoionization cross section, we obtain Pd and Cu partial spectral weights of ${\mathrm{Cu}}_{\mathit{x}}$ ${\mathrm{Pd}}_{1\mathrm{-}\mathit{x}}$ alloys at various compositions (x=0.1, 0.25, 0.5, 0.75, 0.9) using the empirically determined ratio of photoionization cross sections. We find that at this photon energy the photoionization matrix element strongly suppresses structures at the high-binding-energy side of the valence-band spectra where coherent potential approximation calculations predicted appreciable bonding states between Cu 3d and Pd 4d levels. By taking the spectra at the x-ray photoemission regime where this matrix element effect is less severe, we find that the experimental Pd partial spectral weight is in good agreement with theoretical predictions. The lattice relaxation effect does not seem very important for the suppression of Cu 3d and Pd 4d bonding states, at least for concentrated alloys studied here.