PURE ROTATIONAL RAMAN SPECTRA OF DIMETHYLACETYLENE AND DIMETHYLDIACETYLENE
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Date
1978
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Ohio State University
Abstract
The pure rotational Raman spectra of dimethylacetylene-$d_{o}$, dimethylacetylene-$d_{6}$, and dimethyldiacetylene vapor at pressures of 50, 40, and 2 torr, respectively, and excited by the 4579 {\AA}, 4880 {\AA}, and 5145 {\AA} lines of a single mode argon ion laser have been photographed under high resolution. The spectra were recorded on Kodak IIIa-J plates hypersensitized by baking in nitrogen. The spectra of dimethylacetylene-$d_{o}$ and -$d_{6}$ are those of symmetric top rotors, showing the R- and S-branches, whereas in the spectrum of dimethyldiacetylene only the S-branch is observed. The molecular constants are: \begin{eqnarray*} \begin{array}{lllll} H_{3} C-C \equiv C-CH_{3} &:& B_{O} = 0.112 &178(3) cm^{-1},& D_{J} = 3.14(23) \times 10^{-8} cm^{-1}\\ D_{3} C-C \equiv C-CD_{3} &:& B_{O} = 0.088 &871(8) cm^{-1}, &D_{J} = 1.46(12) \times 10^{-8} cm^{-1}\\ H_{3} C-C \equiv C-CH_{3} &:& B_{O} = 0.037 &263(3) cm^{-1}, &D_{J} = 1.12(2) \times 10^{-8} cm^{-1} \end{array} \end{eqnarray*} These constants are averages over the ground state and the low lying vibrational states which are sufficiently populated at room temperature. The quoted errors are one standard deviation. The spectroscopic values of the moments of inertia for dimethylacetyleno-$d_{o}$ and -$d_{6}$ are compared to those computed using the latest electron diffraction data..
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This work was supported in part by a grant from the National Science Foundation data. A. Weber is on sabbatical leave at the National Bureau of Standards, Molecular Spectroscopy Division, Washington, D. C., 20234.""
Author Institution: Department of Physics, Fordham University
Author Institution: Department of Physics, Fordham University