Brune William H, Jenkins Jena M
Department of Meteorology and Atmospheric Science, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
JACS Au. 2024 Nov 22;4(12):4921-4926. doi: 10.1021/jacsau.4c00905. eCollection 2024 Dec 23.
A critical reaction affecting the oxidation chemistry in the middle-to-upper atmosphere occurs between hydroxyl (OH) and hydroperoxyl (HO). The reaction rate coefficient for OH + HO → HO + O, here called , has challenged laboratory kineticists for 50 years. However, several measurements from the past 30 years had approached a rough consensus until the publication of a new study that examined, for the first time, the water vapor dependence of this reaction. According to the study, is not the recommended value of 11.0 × 10 cm molecule s, but instead, a water-dependent (∼1 × 10 + 2.17 × 10[HO]) cm molecule s. Our study examines the water dependence of k using water vapor photolysis of moist air at atmospheric pressure in a flow tube, with direct detection of both OH and HO. The observed OH decays were due only to the OH reaction with HO and, to a lesser extent, the OH loss to the flow tube wall and trace impurities. The resulting k is (8.54 ± 2.90) × 10 cm molecule s, 68% confidence, independent of water vapor and lower than but consistent with the recommended value.
在中层到上层大气中，一种影响氧化化学的关键反应发生在羟基（OH）和氢过氧自由基（HO）之间。OH + HO → HO + O的反应速率系数（这里称为 ），50年来一直困扰着实验室动力学研究者。然而，在一项首次研究该反应对水蒸气依赖性的新研究发表之前，过去30年的几项测量结果已接近大致共识。根据该研究， 并非推荐值11.0×10 cm³分子⁻¹秒⁻¹，而是一个与水有关的值（约1×10⁻¹² + 2.17×10⁻¹²[HO]）cm³分子⁻¹秒⁻¹。我们的研究在流动管中通过对潮湿空气进行水蒸气光解来研究k对水的依赖性，并直接检测OH和HO。观察到的OH衰减仅归因于OH与HO的反应，以及在较小程度上OH向流动管壁和微量杂质的损失。由此得到的k为（8.54 ± 2.90）×10⁻¹² cm³分子⁻¹秒⁻¹，置信度为68%，与水蒸气无关且低于推荐值但与之相符。
