Biomedical Engineering Reference
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and the process is non-adiabatic. Thus, the probability of non-adiabatic transfer is higher,
the smaller the magnitude of the resonance integral, the lower the velocity of nuclear
motion and the smaller the difference in the curvature of the terms. At P = 1 the process is
adiabatic and treated by classical Arhenius or Eyring equations.
The theory predicts a key role by electronic interaction, which is quantitatively
characterized by the value of resonance integral V in forming energetic barrier. If this
value is sufficiently high, the terms are split with a decreasing activation barrier and the
process occurs adiabatically. In another non-adiabatic extreme, where the interaction in the
region of the coordinate is close to zero, the terms practically do not split, and the
probability of transition i f is very low.
Marcus model. Reorganization energy
According to the Marcus model (Marcus, 1968, 1999; Marcus and Sutin 1985), the
distortion of the reactants, products and solvent from their equilibrium configuration is
described by identical parabolas, shifted related to each other according to the driving
force of the value of the process, standard Gibbs free energy (Fig. 2.2). Within the
adiabatic regime (strong electronic coupling, the resonance integral
), the
value of the electron transfer rate constant is
and the Gibbs energy of activation is:
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