Figure 1.

Theoretical driving-force dependence of electron-transfer reactions (T = 295 K). Classical treatment of nuclear rearrangements (blue) based on λ = 0.8 eV.¹⁸ The intersecting parabolas represent reactant (red) and product (green) potential energy surfaces along the reaction coordinate for normal (left), optimized (middle), and inverted (right) driving forces. A quantum mechanical treatment (cyan: one classical mode, λ = 0.5 eV; one quantum mode, λ = 0.3 eV; ℏω = 1500 cm^–1) predicts damped inverted behavior.³²