Ground state relaxation paths

Competitive Ground State Relaxation Paths from Conical Intersection... 

Figure 7.2. Schematic representation of the conical intersection structure for cis-trans isomerization of c -hexatriene and of some of the possible bond-making processes that might occur along different ground-state relaxation paths (by permission from Olivucci et al.. 1994a).

Fig. 11. Conical intersection for intermolecular charge transfer between n-7r pyrazo-line and trimethylamine. Excited-state path (open circles), ground-state relaxation path (open squares). LD is a weak covalent complex, TS indicates the position of the barrier, EX is the exciplex. The values of the relevant structural parameters are given in A.

Fig. 13. The computational methods used for constructing a photochemical reaction path. The full path is computed by joining different MEPs, each one providing information on a specific part of the excited- or ground-state potential-energy surface. The IRD method is used to compute the steepest relaxation directions departing from the FC point (excited-state relaxation) or Cl (ground-state relaxation). The IRC method is used to compute the steepest-descent line defined by the computed IRDs. The CIO method is used to compute the lowest-energy conical intersection point directly. With TSO we indicate the standard transition structure optimization procedure.

The term radiationless deactivation refers to all processes through which electronically excited states undergo relaxation without the emission of photons, and the triplet state of benzophenone is known to undergo deactivation more rapidly in aromatic solvents than in, for example, carbon tetrachloride at room temperature. Evidence for addition of triplet benzophenone to an aromatic solvent has now been adduced in the case of diphenyl ether (Scheme 5). The authors conclude that triplet excited benzophenone adds to an aromatic nucleus to give a diradical which either undergoes chemical reaction (path b) or dissociates to ground state benzophenone (path a) depending upon the nature of the substituents. ... 

---