Transition assisted by dielectric fluctuations

The answer to this dilemma is that the electronic transition can take place if the following conditions are satisfied (1) the energies of the states immediately before and after the transition are equal, and (2) nuclear positions (therefore the nuclear polarization Pn) are fixed. Therefore, this transition can occur only after a fluctuation in the nuclear positions into a configuration in which condition (1) is satisfied. This fluctuation has to occur before the electronic transition took place, namely at constant charge distribution. 

We are therefore interested in changes in solvent configuration that take place at constant solute charge distribution p that have the following characteristics  

Pn fluctuates because of thermal motion of solvent nuclei  

Note that the relations 5 = 2 — djrP P = Pn + Pg are always satisfied per definition. However, in general 2 equality between these quantities holds 

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