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arXiv · 1710.06522

Infrared observation of OC-C2H2, OC-(C2H2)2 and their isotopologues

A. J. Barclay·A. Mohandesi·K. H. Michaelian·A. R. W. McKellar·N. Moazzen-Ahmadia
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Abstract

The fundamental band for the OC-C2H2 dimer and two combination bands involving the intermolecular bending modes nu9 and nu8 in the carbon monoxide CO stretch region are re-examined. Spectra are obtained using a pulsed supersonic slit jet expansion probed with a mode-hop free tunable infrared quantum cascade laser. Analogous bands for OC-C2D2 and the fundamental for OC-DCCH as an impurity are also observed and analysed. A much weaker band in the same spectral region is assigned to a new mixed trimer, CO-(C2H2)2. The trimer band is composed uniquely of a-type transitions, establishing that the CO monomer is nearly aligned with the a-inertial axis. The observed rotational constants agree well with ab initio calculations and a small inertial defect value indicates that the trimer is planar. The structure is a compromise between the T-shaped structure of free acetylene dimer and the linear geometry of free OC-C2H2. A similar band for the fully deuterated isotopologue CO-(C2D2)2 confirms our assignment.

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A. J. Barclay, A. Mohandesi, K. H. Michaelian, A. R. W. McKellar, N. Moazzen-Ahmadia. 2017-10-17. Infrared observation of OC-C2H2, OC-(C2H2)2 and their isotopologues. https://doi.org/10.1080/00268976.2017.1416199

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