THE SUPERPOSITION OF THE LATTICE RADIATION AND REFLECTIVITY SPECTRA OF MOO3, AND PBMOO4 CRYSTALS

The Raman scattering of MoO3 at 300 and 77 K and the infrared reflecti vity spectra of MoO3 at 300 K have been investigated in different scat tering geometries. The Raman spectra of PbMoO4 crystals at 77 K have b een investigated also. The reflectivity spectra of MoO, crystals were calculated for E \ c and E parallel to a. The phonon parameters and th e effective ionic charges of anions and cations for MoO3 and PbMoO4 cr ystals are determined. The diagrams of the splitting of the vibrationa l levels by the Davydov resonance and by the factor group interactions have been determined. It is shown that the lattice radiation of cryst als which have a number of vibrational oscillators (MoO3, PbMoO4) begi ns at low energy vibrational modes and at low values of the damping pa rameters.