Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1250327 | Vibrational Spectroscopy | 2009 | 8 Pages |
Room temperature polarized Raman scattering and infrared reflectance spectra of a NaGd(WO4)2 single crystal have been measured. The IR spectra interpretation was aided by a Kramers-Krönig analysis, and fitted to the independent oscillator model. All 13 theoretically expected Raman-active bands have been identified and assigned, as well as 7 out of 8 expected IR active bands. Splitting of bands in both Raman and IR clearly indicates a lowering of the crystal symmetry due to occupation disorder in the 4a site, that randomly accommodates either an Na+ or a Gd3+ ion. The reflectance IR spectra reveal a spatial dispersion, namely a dependence of the transverse optical (TO) polariton frequencies, on the propagation direction in the crystal. The crystal vibrational modes are correlated to the internal modes of the tungstate group WO42−, and to the internal modes of the molecular skeleton. A detailed correlation map of the symmetry analysis is presented.