Conical intersections double-cone potential energy

In our calculated potential energy surfaces, we have shown that the avoided crossing, which is the transition state for ET in Marcus theory, is a region centered on a conical intersection. The topology is similar to the one shown for the model peaked intersection, and in general cases the reaction will take place on the lower surface of the double cone (Figure... 

Figure 3.1 Schematic representation of photochemical reaction involving a conical intersection. The X axis corresponds toXs the "reaction path," which is a representative coordinate orthogonal to the branching space Xi X2. The Y axis (X1/2) is a compound coordinate, corresponding to a vector that lies in the plane spanned by X, X2. Photoexcitation from the ground-state geometry, GSi, leads to the excited-state potential energy surface at point EXq. The excited-state branch of the reaction coordinate continues to various points on the conical-intersection seam Cl, and CI2. At this point decay occurs in the branching space Xi X2 at the double cone shown inset and the reaction path continues on the ground state toward possible products GSt and GS2. Adapted from Serrano-Perez et al. ...

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