Junaid, Bushiri M; Jayasree, R S; Annamma, John; Nayar, V U(Elsevier, July 27, 2005)
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Abstract:
Polarized Raman spectral changes with respect to temperature were investigated for Pr(BrO3)3·9H2O single crystals. FTIR spectra of
hydrated and deuterated analogues were also recorded and analysed. Temperature dependent Raman spectral variation have been explained
with the help of the thermograms recorded for the crystal. Factor group analysis could propose the appearance ofBrO3 ions at sites corresponding
to C3v (4) and D3h (2). Analysis of the vibrational bands at room temperature confirms a distorted C3v symmetry for the BrO3 ion in the crystal.
From the vibrations of water molecules, hydrogen bonds of varying strengths have also been identified in the crystal. The appearance υ1 mode
of BrO3− anion at lower wavenumber region is attributed to the attachment of hydrogen atoms to the BrO3− anion. At high temperatures,
structural rearrangement is taking place for bothH2Omolecule and BrO3 ions leading to the loss ofwater molecules and structural reorientation
of bromate ions causing phase transition of the crystal at the temperature of 447 K.
Junaid, Bushiri M; Mahadevan Pillai, V P; Pradeep, T; Jayasree, R S; Nayar, V U(Elsevier, 1997)
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Abstract:
FTIR and Raman spectra of FeClMoO4 single crystal and polycrystalline Na2MoO4, Na2MoO4·2H2O and
Na2MoO4·2D2O are recorded and analysed. The band positions for different modes suggest that MoO4 tetrahedron
is more distorted in FeClMoO4. The larger splitting observed for the bending modes and partial retention of
degeneracy of the asymmetric stretching mode indicate that angular distortion is greater than liner distortion in
MoO4 2 ion in FeClMoO4 confirming x-ray data. The non-appearance of the n1 and n2 modes in the IR and partial
retention of the degeneracies of various modes show that MoO4 2 ion retains Td symmetry in Na2MoO4. Wavenumber
values of the n1 mode indicate that the distortion of MoO4 tetrahedra in the four crystals are in the order
FeClMoO4\ Na2MoO4·2H2O\Na2MoO4·2D2O\Na2MoO4. The water bands suggest the presence of two
crystallographically distinct water molecules in Na2MoO4·2H2O. They form strong hydrogen bonds