Distance Dependence of the Reaction Rate for the Reduction of Metal Cations by Solvated Electrons: A Picosecond Pulse Radiolysis Study

The decay of the solvated electron generated by picosecond electron pulse radiolysis is studied by broad-band transient absorption measurements in ethylene glycol solutions containing decimolar concentrations of Cu2+, Ni2+, and Pb2+ metal cations. Analysis of the nonexponential kinetics of the decays reveals molecular parameters of the electron transfer reaction. It is found that the reaction occurs at long distance for Cu2+ solutions and is only limited to contact distance in the case of Ni2+ solutions. The distribution of reaction distance strongly depends on the free enthalpy change of the reactions.