γ Radiolysis of Liquids at High Pressures. VIII. Primary Yields at 8.7 kbar and Reactions of the Hydrated Electron with H2O and H3O+

Abstract

Pressure invariance of the primary yields of water radiolysis (previously established for pressures up to 6.4 kbar) was shown to extend to 8.7 kbar in $\gamma$ radiolysis of both neutral and 0.8N H₂SO₄ solutions. $\mathrm{G(}{\mathrm{H}}_2)$ was measured in $\gamma$ radiolysis of the following deaerated solutions at 25° and pressures in the range 0–8.85 kbar: (a) 3 × 10⁻⁵M NaNO₃ and 0.05M glucose (slightly alkaline); (b) 10⁻³M NaNO₃, 2.3 × 10⁻⁴M HClO₄, and 0.05M glucose. In solution (a) $\mathrm{G(}{\mathrm{H}}_2)$ is determined by a competition for $e_{\mathrm{aq}}^{-}$ between the diffusion‐controlled Reaction [3], $$e_{\mathrm{aq}}^{-}+{\mathrm{NO}}_3^{-}\to {\mathrm{no\; H\; or\; H}}_2,$$ and Reaction [1], $$e_{\mathrm{aq}}^{-}+{\mathrm{H}}_2\mathrm{O}\to \mathrm{H}+{\mathrm{OH}}^{-}.$$ In solution (b) the competition is between Reactions [3] and [2], $$e_{\mathrm{aq}}^{-}+{\mathrm{H}}_3{\mathrm{O}}^{+}\to \mathrm{H}+{\mathrm{H}}_2\mathrm{O}.$$ All H are converted to H₂ by reaction with glucose. With the assumption that pressure dependence of $k_3$ is determined approximately by that of water viscosity, kinetic analysis of the results gives ${\mathrm{\Delta V}}_1^{‡}\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}14.3}{\mathrm{ml\; mole}}^{\text{−1}}$ and ${\mathrm{\Delta V}}_2^{‡}\text{\hspace{0.17em}≈\hspace{0.17em}0}{\mathrm{ml\; mole}}^{\text{−1}}$ . From the value of ${\mathrm{\Delta V}}_2^{‡}$ , the absolute partial molal volume of $e_{\mathrm{aq}}^{-}$ (based on a value of −5.4 ml mole⁻¹ for H⁺) is estimated to be in the range 0–11.3 ml mole⁻¹. With an estimated electrostriction contribution of −3 ml mole⁻¹, the electron cavity volume is in the range 3–14 ml mole⁻¹, as compared to about 100 ml mole⁻¹ in liquid ammonia.