SUPERFAST ELECTRODE-REACTIONS INITIATED BY A SUBPICOSECOND LASER-HEATING OF THE ELECTRON-GAS IN A METAL-ELECTRODE

The dependences of the discharge current density j on the temperature T-e of an electron gas heated in a nonequilibrium manner by laser radi ation and on the overvoltage eta are found in the model of electron an d electron-proton transfer from a metal to a reaction center localized at the interface between the metal and a classically reorganizing med ium. It is shown that, with the growing T-e/T (T is the medium tempera ture); the transfer coefficient alpha = partial derivative lnj/partial derivative eta decreases from 1/2 (for ordinary discharge at T = T-e) to T/T-e much less than 1. Because T-e is determined by the experimen tally altered intensity of the laser radiation and the electrode react ion occurs at a constant T, the values of T-e are found directly from the Tafel dependence of the charge emitted into solution. The dependen ce of the current on T-e obeys the Arrhenius law. The effective activa tion energy is related to the energy of the medium reorganization thro ugh the proton coordinate by a scaling relationship, which makes it po ssible to find their sum from an experimental j vs. T-e dependence. It is shown that the specific feature inherent in the reactions of elect ron-proton transfer, as compared with the outerspheric ones, is the gr owth of the prefactor by a few orders of magnitude with the growing T- e. The growth is caused by the alteration in the proton motion from a quantum mode to a classical one at k(B)T(e) > (h) over bar omega(p), w here omega(p) is the frequency of the proton motion.