Pulse Radiolysis of Liquids at High Pressures. II. Diffusion-Controlled Reactions of the Hydrated Electron

Abstract

For each of 11 presumably diffusion-controlled reactions of eaq−, absolute specific rates were determined by pulse radiolysis at four to seven pressures from atmospheric to 6.4 kbar. The ratio of specific rate at 6.4 kbar to that at 1 atm, followed by the corresponding activation volume in milliliters mole−1, is given in parentheses for each of the reactants: O2 (1.05, −0.2), H2O2 (0.88, 0.5), acrylamide (0.90, 0.4), benzamide (0.95, 0.2), p-nitrophenol (0.84, 0.7), NO3− (1.00, 0.0), S2O82− (1.07, −0.3), Cr(C2O4)33− (1.32, −1.1), Tl+ (0.74, 1.2), Cd2+ (0.75, 1.1), Sm3+ (0.86, 0.6). The Debye equation for specific rate of a diffusion-controlled reaction is used for analysis of the results. Such an analysis suggests that the diffusion coefficient of eaq− changes negligibly (compared to normal ions and molecules) and possibly increases with increase in pressure to 6.4 kbar. With the result for reaction of eaq− with NO3−, certain activation volumes obtained in previous γ-radiolysis studies (by assumption of an activation volume for the NO3− reaction) are corrected, and corrected values of 0 and 3 ml mole−1 are obtained for the partial molal volume and cavity volume, respectively, of an electron in water.