THE RAMAN SCATTERING INTENSITY PARAMETERS OF ACETYLENE
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Date
1990
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Ohio State University
Abstract
The Raman trace scattering cross sections for CH strectching vibration may be described in terms of derivatives of the mean molecular polarizability with respect to the CH stretching internal coordinate. There is in general good aggreement between values for these parameters obtained from experimental absolute intensity studies and those calculated by ab initio qunatum mechanical techniques. In particular, this has been verified for the cases of methane, ethane, n-propane, cyclohexane and ethylene. One apparent exception to this result is acetylene, for which this derivate is calculated to be significantly smaller than the experimental value, when compared with the results for other $molecules.^{1.2}$ We have remeausured the Raman trace and quadrupole scattering cross section for acetylene and re-analysed the experimental results within the double harmonic approximation. The obtained parameters fir the experimental result to a high degree of accuracy, and both the measured cross sections and derived intensity parameters agree well with the previous results. We have also considered the contribution of various approximations made in the ab initio calculattions, When we examined the effect of electron correlation on the calculated ethane, ethylene and accetylen intensity parametress. We found that the accelyene results were effectd differently than those for ethane and ethylene. For these three cases, the ab initio calculations with electron correlation yield CH stretching intensity parameters that more closely parallel those obtained from experiment.
Description
$^{1}$E.N. Svendsen and T. Stroyer-Hansen, Molec, Phys. 56,1025 (1985). $^{2}$K.M. Gough, J. Chem. Phys. 91, 2424 (1989).
Author Institution: Department of chemistry and Biochemistry, University of Guelph; Division of Chemistry, National Research Council of Canada
Author Institution: Department of chemistry and Biochemistry, University of Guelph; Division of Chemistry, National Research Council of Canada