Coupled electronic oscillator representation

Fig. 3.5 Schematic representation of the coupling of two electronic states by an oscillating electric field (q represents an electron in an excited state and q an electron in its ground state). 

The enhancement of the total S value by the CT state coupling can be understood using the simplest possible model of the system two excited electronic states and a single vibrational mode. The first state [Qy exciton state) is assumed to carry all the oscillator strength while the second state,(CT state) is dark. In the diabatic representation, the effective Hamiltonian in the linear vibronic coupling model of the excited state surface can be written as " " ... 

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