Concerted versus stepwise three-body dissociation of sym-triazine: The role of the excited states topology
Excited states derived from excitations between degenerate and non-degenerate MOs exhibit familiar “Mexican hat” shaped Jahn-Teller intersections (green cartoon). Excitations between two pairs of degenerate MOs result in a different topology: four electronic states are scrambled around a D3h intersection yielding PESs that appear glancing rather than conical due to very small linear terms (orange cartoon). EOM-CCSD calculations and the topology analysis of the PESs allowed us to identify the nature of initially populated electronic states in symmetric and asymmetric dissociation of sym-triazine (Tz) induced by charge-exchange between Cs and Tz+ as valence n->p* and Rydberg nR states, respectively.
(Cs-Tz)+ PESs scans and topology around D3h. Kinetic energy of the fragments shown on the right spans multiple excited states. The Dalitz analysis revealed two major dissociation channels: symmetric (orange) within asymmetric (green).