THE SPECTROSCOPY AND INTERNAL TUNNELING DYNAMICS OF THE $C_{2}H_{2}-CO_{2}$ AND $C_{2}H_{2}-N_{2}O$ COMPLEXES: TWO DISTINCTLY DIFFERENT SYSTEM
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Date
1994
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Ohio State University
Abstract
We report the first infrared spectra of the ethylene-carbon dioxide and ethylene-nituous oxide complexes. These rotationally resolved spectra provide detailed information on the equilibrium structures for these complexes, as well as information on the potential energy surface along the coordinate corresponding to the internal rotation of the two molecules relative to one another. In both cases, the rotational constants are consistent with a stacked structure, in which the long axis of the molecules are parallel. The surprising result is that the spectrum of ethylene-carbon dioxide shows sub-bands that are strongly shifted from the expected rigid rotor origins, characteristic of internal rotation, while no such shifts are observed for the ethylene-nitrous oxide case. The differences between these two systems are explained with the aid of {ab initio} calculations of the potential energy surface along the internal rotation coordinate. The rather unique pattern observed for the sub-band origin shifts in the ethylene-carbon dioxide spectrum results from an extremely low barrier to internal rotation and the coincidental relative sizes of the rotational constants of the carbon dioxide and ethylene monomer units.
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Author Institution: Dept of Chemistry, University of N. Carolina