Vibrational spectra of sodium gadolinium tungstate NaGd(WO4)2 single crystals: Observation of spatial dispersion

S. Perets, R. Z. Shneck, R. Gajic, A. Golubovic, Z. Burshtein

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Abstract

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.

Original languageEnglish
Pages (from-to)110-117
Number of pages8
JournalVibrational Spectroscopy
Volume49
Issue number2
DOIs
StatePublished - 18 Mar 2009

Keywords

  • Infrared spectroscopy
  • Kramers-Krönig analysis
  • NaGd(WO)
  • Raman spectroscopy
  • Site occupation disorder
  • Spatial dispersion

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