FREE-JET INFRARED ABSORPTION SPECTROSCOPY OF THE $C_{2}H_{2}-Ar$ COMPLEX IN THE DOUBLY DEGENERATE MONOMER C-H BENDING REGION
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Date
1993
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Publisher
Ohio State University
Abstract
Vibration-rotation transitions of the $C_{2}H_{2}-Ar$ complex have been observed in the doubly degenerate monomer $\nu_{5}$ region via direct IR absorption of tunable diode-laser radiation in a pulsed supersonic free jet. The spectrum is composed of in- and out-of-plane C---H bending bands, which are coupled with each other through a strong b-type Coriolis interaction. Anomalous Coriolis-coupling and A rotational constants indicate the failure in a semirigid-molecule description of this highly nonrigid system in the doubly degenerate bending manifold. A dynamical model calculation, where the large-amplitude vdW bending is treated as an internal rotation of the $C_{2}H_{2}$ subunit hindered by an anisotropic intermolecular potential, has revealed that the characteristic energy--level structure originates from its specific angular momentum coupling scheme involving an additional angular momentum for the intramolecular degenerate bending. The difference potential providing the parity doubling in the C---H bending manifold is estimated to be relatively small, - $-0.1 cm^{-1}$.
Description
Author Institution: Department of Pure and Applied Sciences, The University of Tokyo; Department of Pure and Applied Sciences, The Institute for Molecular Science; Department of Pure and Applied Sciences, RIKEN. The Institute of Physical and Chemical Research; Department of Chemistry, Nagaoka University of Technology