Marcus Parabolic Model for ET

In a symmetric ET reaction, the driving force for ET is absent nevertheless, ET takes place. For example, the following ET reaction is symmetric  

Notice, however, that the vibrational energy levels are of importance at low temperature, particularly for light elements. In that situation. Equation 10.19 depends on the isotope. 

In Section 4.7.1, we found that if the diabatic energy surfaces, Hu and H22, interact with the interaction matrix element, H12, we may approximately write the secular equation 

Hjj and H22 are assumed to be degenerate but with different equilibrium points, corresponding to equivalent but different locations of the electron. 

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