THE $\nu_{5}$ BAND OF $CH_{3}CD_{3}$: HIGH RESOLUTION SPECTRUM AND GLOBAL THREE-BAND ANALYSIS
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Date
2003
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Publisher
Ohio State University
Abstract
The lowest frequency parallel fundamental band $\nu_{5}$ of $CH_{3}CD_{3}$ near $900 cm^{-1}$ was measured at low temperature with a resolution of $0.0021 cm^{-1}$ using Fourier transform spectroscopy. The band is weak, and an absorption path of 60m was used. Large torsional splittings due to inter-vibrational coupling have been observed. Building on previous studies of the torsional levels in the ground vibrational state and and in the methyl rocking state ($\nu_{12} = 1$), a three-band analysis including this most recent data has been completed. The combined data set of more than 2,200 frequencies was fitted to within experimental accuracy using a 43-term model Hamiltonian. The results were found to bear a striking resemblance to those of an earlier, analogous study of $CH_{3}SiH_{3}$. In both cases, Fermi coupling between the ($\nu_{5} = 1$) state and the ground state was found to be the dominant interaction responsible for the observed torsional splittings. Inclusion of this coupling results in a simplification of the ground-state Hamiltonian, so that only eight additional terms were required with the introduction of the $\nu_{5}$ band.
Description
Author Institution: Department of Physics and Astronomy, University of Calgary; Steacie Institute for Molecular Sciences, National Research Council of Canada; Department of Physics and Astronomy, University of British Columbia; Department of Physics and Astronomy, University of Calgary