15min:

JOHN F. STANTON, MITCHIO OKUMURA, 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.

A good argument can be made that the atmospherically relevant NO₃ radical is the most complicated tetraatomic molecule. Five electronic states (the ground X²A₂' state, and the two degenerate A²E'' and B²E' 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 A²E'' state, and a profound pseudo-Jahn-Teller interaction which couples the X²A₂' 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 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 NO₃^- as well as the recent experiments of Okumura and coworkers in which the (dipole forbidden) A²E'' state is accessed by direct absorption from the ground state.