Structures, Vibrational Frequencies, and Bond Energies of the BrHgOX and BrHgXO Species Formed in Atmospheric Mercury Depletion Events
Structures, Vibrational Frequencies, and Bond Energies of the BrHgOX and BrHgXO Species Formed in Atmospheric Mercury Depletion Events
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DOI：
10.1021/acs.jpca.7b06829
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发表时间：
2017-10-19
影响因子：
2.9
通讯作者：
Dibble, Theodore S.
中科院分区：
文献类型：
--
作者：
Jiao, Yuge;Dibble, Theodore S.
极地春季的光化学导致大气汞耗竭事件（AMDE）：Hg（0），通常在大气中存在数月，并且可以在不到一天的时间内损失90%以上。已知这些剧烈的损失主要是由Br + Hg + M -> BrHg中心点+ M引起的，但BrHg中心点的命运是一种猜测。据信，BrHg中心点主要与卤素氧化物XO（X = Cl、Br和I）反应形成BrHgOX化合物，但这些物种从未被实验研究。在这里，我们使用量子化学来表征这些BrHgOX物种及其BrHgXO异构体的结构，振动频率和热力学。BrHgXO异构体以前从未在实验或计算中进行过研究。我们发现BrHgOX物种比它们的BrHgXO异构体更稳定24-28 kcal/mol。当在极性AMDE过程中形成时，BrHgBrO和BrHgIO表现出足够的稳定性，因为它们在经历沉积之前不会解离，但BrHgClO可能不是那么稳定。
Photochemistry during the polar spring leads to atmospheric mercury depletion events (AMDEs): Hg(0), which typically lives for months in the atmosphere, and can experience losses of more than 90% in less than a day. These dramatic losses are known to be initiated largely by Br + Hg + M -> BrHg center dot + M, but the fate of BrHg center dot is a matter of guesswork. It is believed that BrHg center dot largely reacts with halogen oxides XO (X = Cl, Br, and I) to form BrHgOX compounds, but these species have never been studied experimentally. Here, we use quantum chemistry to characterize the structures, vibrational frequencies, and thermodynamics of these BrHgOX species and their BrHgXO isomers. The BrHgXO isomers have never previously been studied in experiments or computations. We find the BrHgOX species are 24-28 kcal/mol more stable than their BrHgXO isomers. When formed during polar AMDEs, BrHgBrO and BrHgIO appear sufficiently stable in that they will not dissociate before undergoing deposition, but BrHgClO is probably not that stable.