The ground and electronically excited states of cyclic are characterized at the equilibrium geometry and along the Jahn-Teller distortions. Lowest excited states are derived from single excitations from the doubly degenerate highest occupied molecular orbitals (HOMOs) to the doubly degenerate lowest unoccupied molecular orbitals (LUMOs), which give rise to two exactly and two nearly degenerate states. The interaction of two degenerate states with two other states eliminates linear terms and results in a glancing rather than conical Jahn-Teller intersection. excitations give rise to two regular Jahn-Teller states. Optimized structures, vertical and adiabatic excitation energies, frequencies, and ionization potential (IP) are presented. IP is estimated to be , in agreement with recent experiments.
REFERENCES
Polar radius and angle are hyperspherical coordinates and , which are similar to the bending and asymmetric stretch normal mode, respectively. For the precise definition stereographic coordinates, see Ref. 12 and references therein.
