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  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 21 (1990), S. 709-716 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared and Raman spectra (5-3500 cm-1) of polycrystalline samples of (C3H7NH3)2PbCl4 and of its deuterated derivative were investigated in the temperature range 90-300 K. An assignment of the observed bands at room temperature is proposed. A temperature dependence study of the frequencies, ν, and half-widths, Δν1/2, of some low-frequency Raman bands revealed two phase transitions at about 110 and 170 K, whereas the deuterated compound showed only one phase transition at about 150 K in the same temperature range. These transitions are believed to be governed by libration of the cation coupled with NH3 group jumps between different potential wells. The value of activation energy, E0 = 3.2 kJ mol-1, was calculated from the plot of Δν1/2 νs. temperature; it is of the same order of magnitude as the potential barrier, V6 = 3.53 kJ mol-1, calculated from the torsional frequency of NH3+ (288 cm-1).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polarized Raman spectra of oriented single crystals of (CH3CH2NH3)2SnCl6 measured over the temperature range 15-300 K have been used to investigate the mechanism of the structural transition at 125 K. A detailed study of some of the external modes and of the internal modes of both the SnCl62- and CH3CH2NH3+ ions in the high- and low-temperature phases has enabled the structure of the disordered high-temperature phase to be confirmed and suggestions for the structure of the low-temperature phase to be proposed.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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