Transient Solvated Electron, Hydroxyl, and Hydroperoxy Radicals in Pulse-Irradiated Crystalline Ice

作者：Irwin A. Taub, Klaus Eiben · 发表于：The Journal of Chemical Physics · 年份：1968 · DOI：10.1063/1.1670446 · 被引用次数：103 · 研究领域：Spectroscopy and Quantum Chemical Studies、Luminescence Properties of Advanced Materials、Atmospheric Ozone and Climate

Neutral, crystalline ice samples were pulse irradiated in order to study phase and temperature effects on the properties of transient intermediates produced in radiolyzed water. These studies demonstrate that optical absorption bands with peaks near 670, at 280 ± 5, and at 230 ± 8 nm are detectable. The transient visible absorption is attributed to a solvated electron es−. Its spectrum, though unaffected by phase change, is influenced by temperature, dEmax / dT being −1.2 × 10−3 eV/deg. Ges− also depends on temperature, decreasing markedly from −5° to −40°C, but only slowly thereafter. The decay of es−, which is second order at −14°C (k = 1.5 × 1011 M−1·sec−1) and partly first order from −40° to −100°C [k(−60°C) = 1.1 × 104sec−1; ΔEact = 9 ± 2 kcal/mole], becomes slower with decreasing temperature. Over-all spectral, yield and kinetic considerations indicate that es− is structurally similar to eaq−, forms via pre-existing traps, and though immobile as a unit, decays both by reaction with H3O+ and by means of an equilibrial, mobile partner em−. These findings are viewed in terms of the polaron theory and other models for the solvated electron. The transient 280-nm absorption is assigned to a hydrogen-bonded hydroxyl radical OHt·. ESR data showing chemical and kinetic characteristics similar to the optical results confirm this assignment. Its molar extinction coefficient at −196°C is estimated as ε280 = 560 ± 50 M−1·cm−1 [using GOHt· (stable) = 0.8]. The over-all OHt· decay is ...