Quantum theory of chemical reactions of the solvated electron

Abstract

The solvated electron represents a more diffuse charge distribution than do electrons in molecules. The electron-exchange integral in rate expressions for reactions of the solvated electron is therefore also more sensitive to a variation in external parameters such as the free energy of the reaction.

We have investigated this effect and have applied the Condon approximation, but we have determined the orbital exponent of the electronic wavefunction (of assumed spherical symmetry) by minimizing the total potential energy with respect to the actual polarization, for which we have also incorporated frequency dispersion, rather than only the equilibrium polarization. For low frequency nuclear modes this causes a more diffuse charge than at equilibrium in the “normal” free-energy region for the electron-transfer reaction, and a more compact charge in the strongly exothermic region. For high-frequency modes the effect is much larger in the strongly exothermic region and of equal importance to other effects which cause a drop in the rate constant in this region.