Electronic Resource
College Park, Md.
:
American Institute of Physics (AIP)
The Journal of Chemical Physics
87 (1987), S. 5477-5482
ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The structures of NaBr, KBr, RbBr, and CsBr in the vapor phase were determined via standard electron diffraction counting techniques with nozzle temperatures ranging from 820–920 K. The data analysis yielded the structure parameters and the ratio of the monomeric to dimeric compounds. The mean amplitudes of vibration for the monomeric molecules were held at values based on microwave frequencies and the harmonic potential approximations. The corrected monomer distances re agree well with microwave–spectroscopy results. Rhombic geometries with bonded dimer distances ranging from 2.74 to 3.37 A(ring) and Br–M–Br angles that ranged from 85° to 101.6° were observed. The percentage of dimer in the vapor was found to vary from 7% to 18%. The most surprising result was the large value obtained for the KBr dimer bonded distance. It is substantially larger than predicted by current theories and is nearly as large as the interionic distance in the crystal. Thermodynamic calculations were performed to allow comparisons of the dimer mole fractions observed with values derived from existing structure models.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.453666
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