ISSN:
0377-0486
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Raman spectra of NH4ReO4 and ND4ReO4 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.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jrs.1250070210
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