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Author(s):Thapaliya, Bishnu P
Contributor(s):Perry, David S.; Bhatta, Ram; Dawadi, Mahesh B.
Subject(s):Vibrational structure/frequencies
Abstract:The Jahn-Teller theorem footnote{H.~A.~ Jahn, and E.~Teller, textit{Proc.~R.~Soc.~Lond.~A.} underline{textbf{161}},~220, (1937).} states that �All non-linear nuclear configurations are therefore unstable for an orbitally degenerate electronic state.� In 1982, Kellman footnote{M.~E.~ Kellman, textit{Chem.~Phys.~Lett.} underline{textbf{87}},~171, (1982).} realized that the Jahn-Teller theorem also applies to nonlinear molecular species in non-degenerate electronic states when there are high-frequency vibrations that are degenerate at a symmetrical reference geometry. When those high frequencies can be considered as adiabatic functions of degenerate low-frequency coordinates, there is a spontaneous Jahn-Teller distortion that lifts the degeneracy of the high-frequency vibrations. Kellman applied the vibrational Jahn-Teller (vJT) concept to the Van der Waals dimer (SF$_{6}$)$_{2}$. In this talk, the vJT concept is applied to E $otimes$ e systems that are small bound molecules in non-degenerate electronic states. The first case considered in systems for which the global minimum of the electronic potential has C$_{3v}$ symmetry.For such systems, including (C$_{6}$H$_{6}$)Cr(CO)$_{3}$ and CH$_{3}$CN, the vJT effect leads to a significant splitting of the degenerate high-frequency vibrations (CH or CO stretches), but the spontaneous vJT distortion is exceptionally small. The second case in systems for which the global minimum of the electronic potential is substantially distorted from the C$_{3v}$ reference geometry. For the second case systems, including CH$_{3}$OH and CH$_{3}$SH, the vJT splitting of the degenerate CH stretches is much larger, on the order of several 10タルs of cm$^{-1}$). For both cases, there is the symmetry-required vibrational conical intersection at the C$_{3v}$ reference geometry. For the second case systems, there are additional symmetry-allowed vibrational conical intersections far from the C$_{3v}$ geometry but energetically accessible to the molecule at thermal energies. For both cases, the vibrationally adiabatic surfaces, including the multiple conical intersections, are well described by modest extensions to a high-order Hamiltonian that was developed for the electronic Jahn-Teller problem.footnote{A.~ Viel, and W.~Eisfeld, textit{J.~Chem.~Phys.} underline{textbf{120}},~4603, (2004).}
Issue Date:25-Jun-15
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:ACS
Date Available in IDEALS:2016-01-05

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