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Title:A zero-order picture of the infrared spectrum for the methoxy radical: assignment of states
Author(s):Johnson, Britta
Contributor(s):Sibert, Edwin
Abstract:The ground $\tilde{X}^2E$ vibrations of the methoxy radical have intrigued both experimentalists and theorists alike due to the presence of a conical intersection at the C$_{3v}$ molecular geometry. This conical intersection causes methoxy's vibrational spectrum to be strongly influenced by Jahn-Teller vibronic coupling which leads to large amplitude vibrations and extensive mixing of the two lowest electronic states. This coupling combined with spin-orbit and Fermi couplings greatly complicates the assignments of states. \medskip Using the potential force field and calculated spectra of Nagesh and Sibert$^{1,2}$, we assign quantum numbers to the infrared spectrum. When the zero-order states are the diabatic normal mode states, there is sufficient mode mixing that the normal mode quantum numbers are poor labels for the final states. We define a series of zero-order Hamiltonians which include additional coupling elements beyond the normal mode picture but still allow for the assignment of Jahn-Teller quantum numbers. In methoxy, the two lowest frequency {\it e} modes, the bend ($q_5$) and the rock ($q_6$), are the modes with the strongest Jahn-Teller coupling. In general, a zero-order Hamiltonian which includes first-order Jahn-Teller coupling in $q_6$ is sufficient for most states of interest. Working in a representation which includes first-order Jahn-Teller coupling in $q_6$, we identify states in which additional coupling elements must be included
these couplings include first-order Jahn-Teller coupling in $q_5$, higher order Jahn-Teller coupling in $q_5$ and $q_6$, and, in the dueterated case, Jahn-Teller coupling which is modulated by the corresponding {\it a} modes. \medskip \begin{list}{}{}\item[$^1$] Nagesh, J.
Sibert, E.~L. {\em J. Phys. Chem. A} {\bf 2012}, {\em 116}, 3846--3855. \item[$^2$] Lee, Y.F.
Chou, W.T.
Johnson, B.A.
Tabor, D.P.
Sibert, E.L.
Lee, Y.P. {\em J. Mol. Spectrosc.} {\bf 2015}, {\em 310}, 57-67. \item[$^2$] Barckholtz, T.~A.
Miller, T.~A. {\em Int. Revs. in Phys. Chem.} {\bf 1998}, {\em 17}, 435--524. \end{list}
Issue Date:2016-06-23
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper/Presentation
Rights Information:Copyright 2016 by the authors
Date Available in IDEALS:2017-01-26

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