USA TUNNELING INTERACTIONS BETWEEN DIFFERENT CONFORMERS IN VIBRATIONALLY EXCITED STATES OF ETHYLPHOSPHINE, $CH_{3}$ $CH_{2}$ $PH_{2}$
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Date
1991
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Ohio State University
Abstract
The microwave spectra of several vibrationally excited states of both the trans and gauche conformers of ethylphosphine have been assigned and analyzed. Most transitions assigned to the gauche conformer are split into two or four components. The larger splittings result from tunneling through the barrier between the equivalent gauche forms. They have been analyzed with an effective Hamiltonian for two state with Coriolis interaction. Energy differences of 229.4, 51 and 6.52 MHz between the symmetric and antisymmetric J=0 levels have been obtained for the first vibrationally excited states of the C-PH$_{2}$ torsion, the C-CH$_{3}$ torsion and the CCP bending vibration, respectively. The smaller splittings are due to methyl group internal rotation for which a barrier of 1050 $cm^{-1}$ has been determined from the excited state of the C-CH$_{3}$ torsion. An additional perturbation is present in the $J_{3,J-2}$ $-J_{2,J-2}$ interstate transition series of these excited states. In the case of the C-PH$_{2}$ torsional excited state, it is caused by a Coriolis-type interaction through the gauche-trans barrier with a vibrationally excited state of the trans conformer whose J=0 level is 1.24 or $1.59 cm^{-1}$ above the antisymmetric J=0 gauche state.
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Author Institution: Department of Chemistry, University of South Carolina