INTERNAL ROTATION IN p-FLUOROTOLUENE AND NITROMETHANE BY HIGH RESOLUTION FTIR SPECTROSCOPY.
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Date
1993
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Ohio State University
Abstract
The barrier to internal rotation of p-fluorotoluene (pFT) and nitromethane (NM) are $4.77 cm^{-1}$ and $2 cm^{-1}$ respectively. Because of the nearly free internal rotation these molecules can be described by the Hamiltonian. $H = AP^{2}_{a} + BP^{2}_{b} + CP^{2}_{C} + F_{p}^{2} - 2A^{\prime} P_{a}P$ together with centrifugal distortion constants for overall and internal rotation. FTIR spectra of a C-type band of pFT at $819 cm^{-1}$ and an A-type band of NM at $917 cm^{-1}$ are analysed for the $m=o$ state transitions to obtain the upper state rotational and centrifugal distortion constants. We have also assigned the vibration-rotation transitions belonging to the torsional states m-1 and 2. A method based on the splitting of R-branch transitions ($^{P}R_{-K} -- ^{R}R_{K}$ for C-type and $^{Q}R_{-K} -- ^{Q}R_{-K}$ for A-type) is proposed for determination of the constant A' and is used for both the molecules.
Description
P. N. Ghosh, J. Mol. Spectrosc.142, 295 (1990).
Author Institution: Department of Physics, University of Calcutta
Author Institution: Department of Physics, University of Calcutta