Figure 25.

(a) Description of coupled PT and ET reactions using a single solvent coordinate Q. The Q values for the states in Figure 20 are indicated. If the reaction mechanism is ET/PT, the change in Q that induces the ET_a process (ΔQ_1a,2a) includes the Q displacement required for the occurrence of PT₁ (ΔQ_1a,1b), but PT occurs following ET. (b) The treatment of Soudackov and Hammes-Schiffer removes the inconsistency in panel a by introducing two different solvent coordinates, x and y, for PT and ET, respectively. Panel b reprinted with permission from ref (191). Copyright 2000 American Institute of Physics.