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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Radiolysis of Aqueous Solutions with Pulsed Ion Beams. 4. Product Yields for Proton Beams in Solutions of Thiocyanate and Methyl Viologen/Formate
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Radiolysis of Aqueous Solutions with Pulsed Ion Beams. 4. Product Yields for Proton Beams in Solutions of Thiocyanate and Methyl Viologen/Formate

机译：脉冲离子束对水溶液的辐射分解。 4.硫氰酸盐和甲基紫精/甲酸酯溶液中质子束的产品收率

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摘要

The yields of radicals from water decomposition produced in the radiolysis of two types of aqueous solutions, thiocyanate and methyl viologen (MV~(2+)), were determined using proton pulses of 5.2 MeV energy. Aerated thiocyanate solutions in the concentration range of 0.001-0.75 M gave yields of (SCN)_2~(·-), formed from scavenging OH radicals, that were lower than those for high-energy electrons and higher than those for ~4He ions of 21 MeV energy. The (SCN)_2~(·-) yield increased with increasing thiocyanate concentration, but the decay of thiocyanate radicals through intratrack reactions appears to be substantial in proton radiolysis. Methyl viologen radical cations (MV~(·+)) formed by scavenging e~(aq)~-, H atoms, and OH radicals were measured in deaerated 0.5 mM MV~(2+) solutions containing formate. The MV~(·+) yields agreed with the results of steady-state proton beam radiolysis, which confirms earlier results that this system is a suitable chemical dosimeter for ion beam pulse radiolysis. The yields of MV~(·+) in deaerated MV~(2+) solutions containing formate and formate/tertiary butanol were used to determine the yields of OH radicals and the sum of the e_(aq)~- and H atom yields. Both sets of yields for proton beams were lower than the corresponding ones for high-energy electrons and higher than those for 21 MeV ~4He ions. The predicted hydroxyl radical yields for proton beams increase with increasing scavenging capacity and approach the value found for high-energy electron radiolysis. The sum of the e_(aq)~- and H atom yields is about 1.8 molecules/100 eV and nearly independent of the scavenging capacity for OH radical. Intratrack reactions were simulated using a deterministic diffusion kinetic model, and the results qualitatively predict the observed yields in the thiocyanate and the MV~(2+) solutions.
机译：使用5.2 MeV能量的质子脉冲测定了两种类型的水溶液（硫氰酸盐和甲基紫精（MV〜（2+）））的辐射分解过程中因水分解而产生的自由基的收率。浓度范围为0.001-0.75 M的充气硫氰酸盐溶液产生的（SCN）_2〜（·-）收率由清除OH自由基形成，低于高能电子的产率，高于〜4He离子的〜4He离子的产率。 21 MeV能量。 （SCN）_2〜（·-）的收率随着硫氰酸盐浓度的增加而增加，但在质子辐解中，硫氰酸盐自由基通过轨道内反应的衰减似乎很大。在含有甲酸酯的脱气的0.5 mM MV〜（2+）溶液中测量了通过清除e〜（aq）〜-，H原子和OH自由基形成的甲基紫罗兰自由基阳离子（MV〜（+））。 MV〜（·+）的产量与稳态质子束辐射分解的结果一致，这证实了较早的结果，该系统是适用于离子束脉冲辐射分解的化学剂量计。用脱气的含甲酸酯和甲酸酯/叔丁醇的MV〜（2+）溶液中的MV〜（·+）的产率确定OH自由基的产率以及e_（aq）〜和H原子的产率之和。两组质子束的产率均低于高能电子的相应产率，且高于21 MeV〜4He离子的产率。质子束的预测羟基自由基收率随着清除能力的增加而增加，并接近高能电子辐射解的发现值。 e_（aq）〜-和H原子的产量之和约为1.8分子/ 100 eV，几乎与OH自由基的清除能力无关。使用确定性扩散动力学模型模拟轨道内反应，结果定性地预测了在硫氰酸盐和MV〜（2+）溶液中观察到的产率。

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