Work terms simple electron transfer

Fick s first and second laws (Equations 6.15 and 6.18), together with Equation 6.17, the Nernst equation (Equation 6.7) and the Butler-Volmer equation (Equation 6.12), constitute the basis for the mathematical description of a simple electron transfer process, such as that in Equation 6.6, under conditions where the mass transport is limited to linear semi-infinite diffusion, i.e. diffusion to and from a planar working electrode. The term semi-infinite indicates that the electrode is considered to be a non-permeable boundary and that the distance between the electrode surface and the wall of the cell is larger than the thickness, 5, of the diffusion layer defined as Equation 6.19 [1, 33] ... 

We have investigated the ferrocene/ferrocenium ion exchange to determine the effects of different solvents on electron-transfer rates. There is probably only a very small work term and very little internal rearrangement in this system. Thus the rates should reflect mostly the solvent reorganization about the reactants, the outer-sphere effect. We measured the exchange rates in a number of different solvents and did not find the dependence on the macroscopic dielectric constants predicted by the simple model [Yang, E. S. Chan, M.-S. Wahl, A. C. J. Phys. Chem. 1980, 84, 3094]. Very little difference was found for different solvents, indicating either that the formalism is incorrect or that the microscopic values of the dielectric constants are not the same as the macroscopic ones. 

The investigation of electron ionization is clearly in the early stages in comparison with the electron transfer studies, and additional work on the influence of orientation on Augmentation will be required before a coherent pattern emerges and a model for fragmentation can be attempted. However, a simple model that considers ionization in terms of the Coulomb potential developed between the electron and the polar molecule, taking the electron transition probability into account, reproduces the main experimental features. This model accounts qualitatively for the steric effect measured and leads to simple, generally applicable, expressions for the maximum (70 eV) ionization cross section. 

Electron transfer from the excited states of Fe(II) to the H30 f cation in aqueous solutions of H2S04 which results in the formation of Fe(III) and of H atoms has been studied by Korolev and Bazhin [36, 37]. The quantum yield of the formation of Fe(III) in 5.5 M H2S04 at 77 K has been found to be only two times smaller than at room temperature. Photo-oxidation of Fe(II) is also observed at 4.2 K. The actual very weak dependence of the efficiency of Fe(II) photo-oxidation on temperature points to the tunneling mechanism of this process [36, 37]. Bazhin and Korolev [38], have made a detailed theoretical analysis in terms of the theory of radiationless transitions of the mechanism of electron transfer from the excited ions Fe(II) to H30 1 in solutions. In this work a simple way is suggested for an a priori estimation of the maximum possible distance, RmSiX, of tunneling between a donor and an acceptor in solid matrices. This method is based on taking into account the dependence... 

There are a number of ways to describe this FC term. An early way of describing the nuclear position and free energy-dependent FC term was proposed in Nobel prize-winning work by Marcus [9, 10]. Marcus approximated the reactant and product, before and after electron transfer, as simple harmonic oscillators with intersecting parabolic potential surfaces. As the driving force of the reaction increases and the product potential surface drops further down in energy, the barrier that must be crossed in going from the bottom of the reactant parabola to the bottom of... 

I spent many years on the study of redox reactions in general before I started to work on the special class of electron transfer reactions. An experiment I did in 1954 — 1 use the personal pronoun because, although I had a coworker, I did most of the laboratory work myself — attracted a great deal of attention to the subject. Ironically, it did not involve electron transfer in the strict sense of the term, but it did introduce a new dimension to the subject of redox reactions of metal ions. It was rather certain at the time that some such reactions of metal-ion complexes do go by simple or overt electron transfer. It was speculated that in other cases, electron transfer could take place by an atom bridging two metal centers in the act of electron transfer, the bridging atom then being transferred from one metal to the other. My contribution was the unequivocal experimental demonstration that it really can occur. 

Here, k is the electronic transmission coefficient (k = 1 for adiabatic electron transfer) and v x the nuclear frequency factor, whereas is the equilibrium constant for assembly of a precursor state and effectively includes any coulombic work and medium (Debye-Hiickel) terms [4, 5]. Following the approach taken by Stranks [7], the observed volume of activation AV for a simple, adiabatic, outer-sphere, bimolecular electron transfer reaction can be represented as... 

First of all, note that the term "oxidation" is based on a historical premise that is not relevant from a more modem perspective namely, the combining of another element with oxygen to form a simple binary compounds i.e., an "oxide" similarly, the removal of oxygen atoms from an oxide molecule leaving the "reduced" element was the concept intended for the term "reduction". Although this idea works fairly well for many of the more simple interactions of oxygen with both metal and non-metal elements, a better, more comprehensive, definition that includes similar reactions with other elements, such as fluorine and chlorine, evolved that was based on the transfer of electrons from one atom (or ion) to another. 

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