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Raman studies of the vibrational dynamics and phase transitions in uranyl nitrate hexahydrate
Author(s) -
Khulbe P. K.,
Agarwal Anshu,
Raghuvanshi G. S.,
Bist H. D.,
Hashimoto H.,
Kitagawa T.,
Little T. S.,
Durig J. R.
Publication year - 1989
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.1250200503
Subject(s) - raman spectroscopy , uranyl , chemistry , phase transition , raman scattering , uranyl nitrate , analytical chemistry (journal) , phase (matter) , atmospheric temperature range , crystallography , materials science , thermodynamics , ion , physics , uranium , organic chemistry , chromatography , optics , metallurgy
The temperature‐dependent Raman spectra of crystalline uranyl nitrate hexahydrate, UO 2 (NO 3 ) 2 · 6H 2 O, are reported in the temperature range 15‐290 K. A group theoretically consistent assignment of the bands in terms of UO 2 2+ , NO 3 − and H 2 O vibrations is proposed. The temperature‐dependent studies of thermosensitive bands associated with these entities were used to study the previously reported phase transition at 140 ± 5 K and to detect another phase transition at 190 ± 5 K. The latter transition shows up prominently in the temperature‐dependent fluorescence studies and is also accompanied by a sharp increase in the Rayleigh scattering. The transition at 190 ± 5 K is triggered by the dynamics of H 2 O‐II and UO 2 2+whereas that at 140 ± 5 K is associated with the dynamics of H 2 O‐II/NO 3 − . Both the transitions are of second order.