High-energy electron transfer products

The technique has been described in detail elsewhere. [26] In short, a pulse of high energy electrons induces a series of chemical reactions that can be monitored, e.g., using time resolved UV-vis spectroscopy. The reaction of interest is usually induced by a reaction between a radical formed from radiolysis of the solvent (usually water) and a solute molecule. The primary radiolysis products in aqueous solution are HO, e q", H, HjOj, H2 and The major radical species, HO and e q, are formed in equimolar concentrations, 0.28 ol/J each, on electron or y-irradiation.[27] As can be seen in reaction 2, the hydroxyl radical does not yield a benzene radical cation instantly upon reaction with a substituted benzene. For this reason, secondary oxidants, such as S04, Brj and N3, are usually used to generate benzene radical cations. To determine one-electron reduction potentials of radical cations, the redox equilibrium between the radical cation of interest and a redox couple with a known one-electron reduction potential is studied. The equilibrium constant can be derived from the rate constants of the electron-transfer reaction and the back reaction and/or the equilibrium concentrations of the two redox couples (reaction 6).[28]... 

In the quantum mechanical formulation of electron transfer (Atkins, 1984 Closs et al, 1986) as a radiationless transition, the rate of ET is described as the product of the electronic coupling term J2 and the Frank-Condon factor FC, which is weighted with the Boltzmann population of the vibrational energy levels. But Marcus and Sutin (1985) have pointed out that, in the high-temperature limit, this treatment yields the semiclassical expression (9). 

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