Optical properties and electronic structures of layered MoO₃single crystals

Reflectivity spectra of layered MoO 3 single crystals have been measured at 6 K in a wide energy range up to 25 eV. The spectra exhibit remarkable anisotropy for the polarization E ∥ c and E ∥ a . Optical constants have been derived through the Kramers-Kronig analysis. The fundamental absorption tail located below 3.7 eV displays an exponential dependence on photon energy for both polarizations. It is found that two luminescence bands peaking at 2.93 and 3.58 eV are stimulated under the excitation with photons in the fundamental absorption region. Their decay behaviours are also examined at 8 K. With use of the discrete variational Xα (DV Xα) method, the electronic structure of an embedded [MoO 4 ] cluster has been calculated for better understanding of the optical properties of MoO 3 . The calculated results are favourably compared with the experimental data.