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The temperature dependence of the Raman spectrum of ammonium perrhenate
Author(s) -
KorppiTommola J.,
Devarajan V.,
Brown R. J. C.,
Shurvell H. F.
Publication year - 1978
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250070210
Subject(s) - perrhenate , raman spectroscopy , chemistry , ion , wavenumber , ammonium , lattice (music) , diffraction , observable , normal mode , phase transition , condensed matter physics , vibration , optics , physics , organic chemistry , quantum mechanics , acoustics
Raman spectra of NH 4 ReO 4 and ND 4 ReO 4 have been recorded at several temperatures between 77 K and 353 K. As the temperature is increased, several bands due to both internal and external modes of the perrhenate ion are shifted to lower wavenumbers and there is a discontinuity in the slope of the wavenumber versus temperature curves near 200 K. This behaviour is correlated with recent NQR and X‐ray diffraction results and supports the suggestion of a higher order phase transition near 200 K. The bands due to the ammonium ion vibrations are broadened as the temperature is increased and the librational lattice mode is no longer observable above about 200 K. The nature of the motion of the ammonium ion in the lattice is discussed and it is pointed out that the presence of a librational lattice mode does not necessarily indicate an absence of reorientational motion.