The kinetics of non-adiabatic bond-breaking electron transfer reactions have been investigated theoretically, taking tert-butyl chloride as a model system. The reaction rate was calculated from first-order perturbation theory. Since the model requires the overlaps between the initial and the final states, the potential-energy surfaces of (CH3)(3)C-Cl and of the dissociating (CH3)(3)C-Cl- system were obtained from quantum-chemical calculations. The calculated points could be represented by a simple analytical form whose parameters were fitted to the data, and from these the wavefunctions for both bound and unbound states were obtained numerically. The overlaps between the lower initial states and the final states appear to be very small for this system, and higher excited states are found to make a significant contribution to the rate, especially for low overpotentials. The activation energy is lower than that obtained from classical models, and corresponds to the excitation energy of levels that contribute most to the reaction rate. (C) 2003 Elsevier B.V. All rights reserved.