Optical properties and electronic structures of layered MoO3 single crystals

Reflectivity spectra of layered MoO3 single crystals have been measured at 6 K in a wide energy range up to 25 eV. The spectra exhibit remarkable anis otropy for the polarization E parallel to c and E parallel to a. Optical co nstants have been derived through the Kramers-Kronig analysis. The fundamen tal 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 a lso examined at 8 K. With use of the discrete variational X alpha (DV X alp ha) method, the electronic structure of an embedded [MoO4] cluster has been calculated for better understanding of the optical properties of MoO3. The calculated results are favourably. compared with the experimental data.