Optical dielectric response of PdO

The dielectric response functions of single-crystal PdO parallel and perpendicular to the c axis are obtained from 1.6 to 5.8 eV by analysis of ellipsometric data. Strong anisotropy is observed. Both ${\mathrm{\varepsilon }}_{\mathrm{\parallel }}$(ω) and ${\mathrm{\varepsilon }}_{\mathrm{\perp }}$(ω) show a Lorentz-oscillator-type resonance near 2.5 eV, but the strength of this oscillator for ${\mathrm{\varepsilon }}_{\mathrm{\parallel }}$ is about twice as big as that for ${\mathrm{\varepsilon }}_{\mathrm{\perp }}$. A simple classical model is used to calculate the Raman excitation profile associated with this oscillator. The result is in good agreement with recent resonance Raman data on PdO. A pair of weak, narrow features near 3.9 eV and a strong broad resonance near 5.8 eV are also observed, and these appear only in ${\mathrm{\varepsilon }}_{\mathrm{\perp }}$(ω).