Reactions of the hydrated electron

The rate constants for the reaction of the hydrated electron e_aq^- with a number of solutes and with radicals formed in water radiolysis are reported. Hydrated electrons were formed in the electron pulse irradiated solutions at concentrations in the range from 1 to 10 μM. Their reaction was followed by the decay of the optical absorption of e_aq^- at 5780 Å. Generally a 0.4 μsec pulse of 15 MeV electrons was used. In the absence of e_aq^- scavengers, second-order kinetics prevailed owing to the dominance of the reactions, e_aq^- + e_aq^-, e_aq^- + H, and e_aq^- + H₂O₂ when OH radical scavengers were present in alkaline solution. An analysis of the decay curves leads to values for ^ke_aq^- + e_aq^- and ^ke_aq^- + H of 0.9 × 10¹⁰ and 3 × 10¹⁰ M^-1 sec^-1, respectively. With scavenger present in excess over [e_aq^-], pseudo first-order kinetics were found and rate constants for a number of inorganic and organic compounds are reported. The agreement of these and other rate constants with diffusion-controlled reaction theory is discussed.