THE INFRARED SPECTRUM OF Ar-HCCH REVISITED
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Date
1991
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Ohio State University
Abstract
The infrared spectrum of the argon---acetylene van der Waals complex has been re-investigated in the three micron wavelength region. Two bands, corresponding to the $v_{3}$ and $v_{2}+v_{4}+v_{5}$ Fermi diad of the monomer, have been recorded. The infrared data were combined with recently published ground state microwave data in a least squares analysis using the Watson S reduction of the asymmetric top Hamiltonian. Some general features of the rotational constants obtained include: very large, positive inertial defects; a large decrease in A on going from the ground to the excited vibrational states; and inverted K=2 asymmetry doublels in the excited states. This last feature, where the $J_{2,J-1}$ energy levels lie above the $J_{2,J-2}$ levels, is caused by $d_{2}=-0.18$ MHz. All of these features are related to large amplitude motions, which are being analyzed in a dynamic model which couples internal rotation of the HCCH monomer with the overall rotation of the complex.
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Author Institution: Dept. of Chemistry, University of Rochester