Adiabatic electrochemical electron-transfer reactions involving frequency changes of inner-sphere modes

A Hamiltonian model is formulated for electrochemical electron-transfer rea ctions involving frequency changes of the inner-sphere modes. The adiabatic free energy surface is calculated and it is shown that this nonlinear coup ling leads to a transfer coefficient different from 1/2, and that the trans fer coefficient can no longer be identified with the electron occupation pr obability in the transition state saddle point, as in the linear coupling c ase. (C) 1999 Elsevier Science S.A. All rights reserved.