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 ε_∥({ω}) and ε_⊥({ω}) show a Lorentz-oscillator-type resonance near 2.5 eV, but the strength of this oscillator for ε_∥ is about twice as big as that for ε_⊥. 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 ε_⊥({ω}).