Harmonic oscillators, electron exchange

We consider first the outer-sphere electron-exchange reactions using a harmonic oscillator model for the solvent /40/ i.e., by assuming that the solvent molecules make small vibrations (restricted rotations)with the same effective frequency V The two ions are treated as two hard spheres /40a/ with different chargesjbeing stationary at a fixed separation (r = const) during the solvent fluctuation, which is necessary for the electron transfer. This means that the relative motion of the two ions is so slow that the vibrations of solvent medium change adiabatically in the course of the reaction. This adiabatic approximation implies that the ions are much heavier than the solvent molecules. 

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