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Some aspects of the radiation chemistry of aqueous solutions of nitrous oxide Head, David Alan


Deaerated acidic, neutral, and basic aqueous N₂0 solutions were irradiated with Co-60 γ -rays in order to: 1) determine the primary yields, and 2) resolve anomalies in relative rate constant ratios of the type k(e⁻aq +S)/k(e⁻aq +N₂0). The yields of the gaseous products N₂, 0₂, and H₂ were determined as a function of both pH and [N₂0]. About 10⁻² M N₂0 is commonly used to evaluate relative rate constant ratios, but this [N₂0] scavenges not only hydrated electrons (e⁻aq ) but also another species, X, (where G(X) = 0.65±0.1), resulting in erroneous rate constant ratios. Yields of primary species found were: Ge⁻aq = 2.4±0.1, G H₂O* ̴ 1.6, and G,H₂⁺, = 0.35±0.05. Kinetic competition studies of the reaction of N₂0 and H⁺ with e⁻aq were undertaken in the concentration ranges 3 x 10⁻⁵ to 2 x 10⁻⁴ M H⁺ and 10⁻⁴ to 10⁻³ M N₂O. The results cannot be explained by: 1) simple competition; 2) charge transfer, or 3) two species being scavenged. They may be explained by assuming a conversion of N₂O to another species in acid solution. This acid species, suggested to be H₂N₂O₂, is apparently five times less reactive toward e⁻aq than is N₂0 in neutral solution. Deaerated neutal N₂0 solutions were irradiated at extremely high intensity with very short pulses of 0.52 Mev electrons. The yields of the gaseous products N₂, O₂, and H₂ were studied in order to examine an expected decrease in solute products, and to determine primary yields at high dose rates. As predicted, significant scavenging occurs for high dose rates only at N₂0 concentrations an order of magnitude larger than those at low dose rates. Also the scavenging, which is complete at ~ 10⁻² M N₂O for low intensity irradiations, is not complete at 2.6 x 10⁻² M N₂0 for high intensity irradiations. These results indicate that the radiation yield of scavengable hydrated electrons is significantly larger at the high intensity used. The yield of hydrogen in pure water (G(H₂) = 1.15±0.2) can be explained on the basis of inter-spur reactions of e⁻aq, H, and OH.

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