INFRARED SPECTRA OF CS$_2$ TRIMER: OBSERVATION OF AN ISOMER WITH $D_3$ SYMMETRY
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Date
2011
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Publisher
Ohio State University
Abstract
Infrared spectra of carbon disulfide trimer formed in a pulsed supersonic slit-jet expansion are obtained via direct absorption of a tuneable diode laser in the region of the CS$_2$ $\nu_3$ fundamental band ($\sim$ 1535 cm$^{-1}$). Two bands sharing the same lower state were assigned to (C$^{32}$S$_2$)$_3$. These correspond to the two infrared active vibrations (a parallel and a perpendicular band) of the constituent CS$_2$ asymmetric stretches. The weaker perpendicular band is centered at 1524.613 cm$^{-1}$. It is shifted by $-$10.74 cm$^{-1}$ with respect to the free CS$_2$ monomer. The parallel band which is significantly stronger is centered at 1545.669 cm$^{-1}$. It has a vibrational shift of $+$10.31 cm$^{-1}$. The transitions with $K\neq 3n$ and those with $J=$ odd and $K=0$ in the ground state are absent in both bands. This rigorously establishes that this isomer of carbon disulfide trimer has $D_3$ symmetry. Thanks to the symmetry, only two parameters, the C-C distance and the angle between a monomer axis and the plane containing the C atoms, are required to fully define the structure of the trimer. These were determined to be 3.811 {\AA} and 61.8$^irc}$, respectively. In addition, a parallel band corresponding to a single $^{34}$S substitution was observed around 1544.46 cm$^{-1}$. Results from this band are in complete agreement with those of the two bands for (C$^{32}$S$_2$)$_3$.
Description
Author Institution: Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N; 1N4, Canada; Steacie Institute for Molecular Sciences, National Research Council of; Canada, Ottawa, ON K1A 0R6, Canada