量子扩散限制氢原子隧穿反应的特征<a href="#fn1" title="提供电子补充信息（ESI）。参见DOI：10.1039 / c7cp05064j">†</a>,Physical Chemistry Chemical Physics

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量子扩散限制氢原子隧穿反应的特征 †
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2017-11-30 00:00:00 , DOI: 10.1039/c7cp05064j
Morgan E. Balabanoff _{1,

2,

3,

4} , Mahmut Ruzi _{1,

2,

3,

4} , David T. Anderson _{1,

2,

3,

4}

Affiliation

我们正在研究掺杂有化学物质的高浓对氢（pH ₂）量子固体中氢原子（H原子）量子扩散的细节，以便更好地了解在这些条件下H原子的运输和反应性。在这项工作中，我们介绍了在固体pH _2中分离出的193 nm甲醇（CH ₃ OH）光诱导化学反应的动力学研究。在1.8 K处对CH ₃ OH进行短期照射很容易产生CH ₂ O和CO，我们可以使用FTIR光谱仪对其进行检测。该原位光化学还生产CH ₃ O和H原子，我们可以从后光解反应动力学可显示显著CH推断₂OH增长。CH ₂ OH的生长动力学表明，至少有三个独立的隧穿反应起作用。（i）光产生的CH ₃ O与pH ₂主体的反应，（ii）H原子与CH ₂ O光片段的反应，以及（iii）H原子的长程迁移和与CH ₃ OH的反应。我们分配的快速CH ₂ OH生长于以下CH ₃ ö+ H ₂ →CH ₃ OH + H→CH ₂ OH + H ₂通过进行使用氘化甲醇类似动力学测量两步连续隧穿机制（CD ₃OD）。通过在1.8和4.3 K下进行光解实验，我们显示了在这个小温度范围内，光解后反应动力学发生了质的变化。我们利用反应动力学随温度的这种定性变化来确定受量子扩散限制的反应。尽管这些结果是特定于pH ₂量子固体中存在的条件的，但它们对发生在金属表面和星际晶粒上的类似的低温H原子隧穿反应具有直接影响。

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Signatures of a quantum diffusion limited hydrogen atom tunneling reaction†

We are studying the details of hydrogen atom (H atom) quantum diffusion in highly enriched parahydrogen (pH₂) quantum solids doped with chemical species in an effort to better understand H atom transport and reactivity under these conditions. In this work we present kinetic studies of the 193 nm photo-induced chemistry of methanol (CH₃OH) isolated in solid pH₂. Short-term irradiation of CH₃OH at 1.8 K readily produces CH₂O and CO which we detect using FTIR spectroscopy. The in situ photochemistry also produces CH₃O and H atoms which we can infer from the post-photolysis reaction kinetics that display significant CH₂OH growth. The CH₂OH growth kinetics indicate at least three separate tunneling reactions contribute; (i) reactions of photoproduced CH₃O with the pH₂ host, (ii) H atom reactions with the CH₂O photofragment, and (iii) long-range migration of H atoms and reaction with CH₃OH. We assign the rapid CH₂OH growth to the following CH₃O + H₂ → CH₃OH + H → CH₂OH + H₂ two-step sequential tunneling mechanism by conducting analogous kinetic measurements using deuterated methanol (CD₃OD). By performing photolysis experiments at 1.8 and 4.3 K, we show the post-photolysis reaction kinetics change qualitatively over this small temperature range. We use this qualitative change in the reaction kinetics with temperature to identify reactions that are quantum diffusion limited. While these results are specific to the conditions that exist in pH₂ quantum solids, they have direct implications on the analogous low temperature H atom tunneling reactions that occur on metal surfaces and on interstellar grains.

更新日期：2017-11-30

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