NO$_3$ STATES ACCESSED BY PHOTODETACHMENT AND DARK-STATE SPECTROSCOPY: WHAT DO WE KNOW?
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Date
2005
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Ohio State University
Abstract
A good argument can be made that the atmospherically relevant NO$_3$ radical is the most complicated tetraatomic molecule. Five electronic states (the ground ${\tilde{X}}^2A_2'$ state, and the two degenerate ${\tilde{A}}^2E''$ and ${\tilde{B}}^2E'$ states) lie within 2 eV, and are coupled by several strong interactions. Amongst these is a strong linear and quadratic Jahn-Teller effect in the ${\tilde{A}}^2E''$ state, and a profound pseudo-Jahn-Teller interaction which couples the ${\tilde{X}}^2A_2'$ ground state with the second excited state. The latter is almost strong enough to break the $D_{3h}$ equilibrium symmetry of the ground state, and severely perturbs vibrational levels associated with the two in-plane modes of $e'$ symmetry. This talk will report {\it ab initio} calculations based on the equation-of-motion coupled cluster model, its application to parametrize various vibronic model Hamiltonians, and simulations of the photodetachment spectrum of NO$_3^-$ as well as the recent experiments of Okumura and coworkers in which the (dipole forbidden) ${\tilde{A}}^2E''$ state is accessed by direct absorption from the ground state.
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Author Institution: Institute; for Theoretical Chemistry, Department of Chemistry, University of Texas at; Austin, Austin, TX 78712; Arthur Amos Noyes Laboratory of Chemical Physics,; California Institute of Technology, Pasadena CA 91125