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Proceedings Paper

Study Of Anharmonic Vibrations By Low Frequency FT-IR Spectroscopy
Author(s): J. R. Durig; T. S. Little; G . A. Guirgis
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Paper Abstract

Our research efforts in the area of anharmonic vibrations, which include the skeletal bending modes in quasilinear molecules, the ring puckering and ring bending modes in four- and five-membered rings, and the torsional modes for molecules with two internal C3, rotors, have been concentrated more recently on the determination of the asymmetric potential function governing the internal rotation in a number of three-membered ring carbonyl compounds, substituted allylic compounds, propenoyl halides and alkyl halides. Although asymmetric potential functions had been previously proposed for some of these molecules, relatively few of these can be given a significant level of confidence due to a number of experimental problems which have been previously encountered. For example, far infrared spectroscopy has been used in the past for the determination of asymmetric torsional frequencies but we have found that a resolution of at least 0.1 cm-1 needs to be used to record the low frequency data because many torsional bands are extremely sharp and therefore were not even observed with the relatively low resolution utilized. Additionally, insufficient resolution may result in misleading relative intensities of the Q-branches so that incorrect assignments have resulted. In many cases, due to symmetry, both infrared and Raman spectroscopic results are needed to identify the high and low energy conformers. Examples will be provided to demonstrate how asymmetric torsional data can be used to obtain potential constants.

Paper Details

Date Published: 20 December 1985
PDF: 2 pages
Proc. SPIE 0553, Fourier and Computerized Infrared Spectroscopy, (20 December 1985); doi: 10.1117/12.970868
Show Author Affiliations
J. R. Durig, University of South Carolina (United States)
T. S. Little, University of South Carolina (United States)
G . A. Guirgis, University of South Carolina (United States)

Published in SPIE Proceedings Vol. 0553:
Fourier and Computerized Infrared Spectroscopy
David G. Cameron; Jeannette G. Grasselli, Editor(s)

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