Shift of conical intersection and replacement by avoided crossing

3 Shift of conical intersection and replacement by avoided crossing 

Nonadiabatic electronic transitions are of fundamental importance in chemistry. In particular, because a conical intersection (conical intersection) between two electronic states provides a very fast and efficient pathway for radiationless relaxation [117], there has been much interest in controlling transitions through a conical intersection. Indeed, several methods have already been proposed to control the dynamical processes associated with a conical intersection. One of these concerns the modification of electronic states involved in the conical intersection by environmental effects of polar solvents on the PES (potential energy hypersurface) through orientational fluctuations [6, 67, 68]. Another strategy is to apply a static electric field to shift the energy of a state of ionic character as in the Stark effect ]384, 482] (see Ref. ]403, 404] for the non-resonant dynamical Stark effect). More dynamical methods, which aim to suppress the transition either by preparing 

The description of our control scheme for transformation of a symmetry-allowed conical intersection to an avoided crossing in the region of the conical intersection begins with a two-state model. The Hamiltonian for n nuclei in a molecular system with a nonadiabatic interaction between two electronic states can be written in the diabatic representation as 

In Sec. 5.4.3, conversion of the conical intersection between the lowest two A states of the NO2 will be taken up as a concrete example. 

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