Rate constants for the reaction of eaq- with N2O, NO3-, NO2-, phenol, SeO42-, S2O32- and Mn2+ have been measured in the temperature range 20-200 °C by pulse radiolysis. In each case non-linear Arrhenius behaviour of the rate constant has been observed for the activation-controlled part of the overall process of diffusion and reaction. The activation energies (E)a decrease with increasing temperature and, except for Mn2+, become negative. The data are interpreted in terms of a model for reversible electron transfer which implies that activation-controlled reactions of e-aq may be reversible. In the case of Mn2+, Ea first decreases and then increases with increasing temperature. It is suggested that a second channel becomes operative at elevated temperatures for the reaction of eaq- with Mn2+.
