ISM as a criterion for solute-driven electron transfers

The energy barrier of the Fe(Cp)2/Fe(Cp 2 self-exchange can also be explored with the ISM, under the approximations discussed in Chapter 15 for the use of this model in the calculation of Franck-Condon factors. According to ISM, the sum of bond distortions from the equilibrium to the transition-state configuration is, for a self-exchange reaction 

The transition-state energy for a self-exchange is given by 

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