Driving force dependence of the nonadiabatic rate constant for the PCET (black), PT (red), and ET (blue) models. In the PCET model, λ = 20 kcal/mol, ω = 3000 cm−1, and δx = 0.5 Å. In the PT model, λ = 5 kcal/mol, ω = 3000 cm−1, and δx = 0.5 Å. In the ET model, λ = 20 kcal/mol, ω = 400 cm−1, and δx = 0.1 Å. The reduced mass of the vibrational mode is 1 amu for PCET and PT and 10 amu for ET. The proton transfer is assumed to be electronically nonadiabatic for all models. The temperature is 300 K, and is the rate constant for ΔG0 = 0.