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首页> 外文期刊>RSC Advances >Self-radiolysis of tritiated water. 4. The scavenging effect of azide ions (N3?) on the molecular hydrogen yield in the radiolysis of water by 60Co γ-rays and tritium β-particles at room temperature
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Self-radiolysis of tritiated water. 4. The scavenging effect of azide ions (N3?) on the molecular hydrogen yield in the radiolysis of water by 60Co γ-rays and tritium β-particles at room temperature

机译：ti水的自辐射分解。 4， 60 Coγ射线对水分解中叠氮离子（N 3 ？）对分子氢产率的清除作用和triβ粒子在室温下

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The effect of the azide ion N3? on the yield of molecular hydrogen in water irradiated with 60Co γ-rays (～1 MeV Compton electrons) and tritium β-electrons (mean electron energy of ～7.8 keV) at 25 °C is investigated using Monte Carlo track chemistry simulations in conjunction with available experimental data. N3? is shown to interfere with the formation of H2 through its high reactivity towards hydrogen atoms and, but to a lesser extent, hydrated electrons, the two major radiolytic precursors of the H2 yield in the diffusing radiation tracks. Chemical changes are observed in the H2 scavengeability depending on the particular type of radiation considered. These changes can readily be explained on the basis of differences in the initial spatial distribution of primary radiolytic species (i.e., the structure of the electron tracks). In the “short-track” geometry of the higher “linear energy transfer” (LET) tritium β-electrons (mean LET ～5.9 eV nm?1), radicals are formed locally in much higher initial concentration than in the isolated “spurs” of the energetic Compton electrons (LET ～0.3 eV nm?1) generated by the cobalt-60 γ-rays. As a result, the short-track geometry favors radical–radical reactions involving hydrated electrons and hydrogen atoms, leading to a clear increase in the yield of H2 for tritium β-electrons compared to 60Co γ-rays. These changes in the scavengeability of H2 in passing from tritium β-radiolysis to γ-radiolysis are in good agreement with experimental data, lending strong support to the picture of tritium β-radiolysis mainly driven by the chemical action of short tracks of high local LET. At high N3? concentrations (>1 M), our H2 yield results for 60Co γ-radiolysis are also consistent with previous Monte Carlo simulations that suggested the necessity of including the capture of the precursors to the hydrated electrons (i.e., the short-lived “dry” electrons prior to hydration) by N3?. These processes tend to reduce significantly the yields of H2, as is observed experimentally. However, this dry electron scavenging at high azide concentrations is not seen in the higher-LET 3H β-radiolysis, leading us to conclude that the increased amount of intra-track chemistry intervening at early time under these conditions favors the recombination of these electrons with their parent water cations at the expense of their scavenging by N3?.
机译：叠氮化物离子N 3 ？ 对照射的水中分子氢产率的影响利用蒙特卡洛轨道化学模拟在25°C下研究了 60 Coγ射线（〜1 MeV康普顿电子）和triβ电子（〜7.8 keV的平均电子能量）。结合可用的实验数据。 N 3 ？ 被证明会干扰H 2 通过对氢原子的高反应性，但对水合电子的反应程度较小，H 2 的两种主要辐射前体在扩散中产生辐射轨迹。在H 2 可清除性中观察到化学变化，具体取决于所考虑的辐射类型。这些变化可以根据主要辐射分解物种（即，电子径的结构）的初始空间分布的差异轻松解释。在较高的“线性能量转移”（LET）ββ电子的“短轨道”几何中（平均LET〜5.9 eV nm ？1 ），自由基是由钴60γ-产生的高能康普顿电子的孤立“杂散”（LET〜0.3 eV nm ？1 ）中的初始浓度要高得多。射线。结果，短径几何结构有利于涉及水合电子和氢原子的自由基自由基反应，从而导致β<-> 2 的产率明显增加。电子与 60 Coγ射线相比。 H 2 从tri-辐射到γ辐照的清除能力的这些变化与实验数据吻合良好，为，β的图像提供了有力的支持。 -辐射分解主要是由高局部LET的短轨道的化学作用驱动的。在高N 3 ？ 浓度（> 1 M）下，我们的H 2 < 60 Coγ辐射的/ sub> 收率结果也与以前的蒙特卡洛模拟相一致，该模拟表明必须将捕获的前体包括在内。 N 3 ？生成水合电子（ ie ，即水合之前的短暂“干燥”电子）？ 。如实验所观察到的，这些过程倾向于显着降低H 2 的产量。然而，在较高的LET 3 Hβ辐射分解中未观察到高叠氮化物浓度下的这种干电子清除作用，这使我们得出结论，道内量增加在这些条件下早期进行化学干预，有利于这些电子与母体水阳离子的重组，但会牺牲N 3 ？< / sup> 。

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