Theoretical Investigations of OH/HO2 Chemistry in the Middle Atmosphere

在本项目中，将对平流层上层和中层下层的OH/HO2化学相关的一些突出问题进行研究。目前对大气中这一区域HOx化学的理解是复杂的，因为标准的光化学模型或对它们的任何修改都不能一致地解释平流层顶上下奇怪的氢丰度。这部分是由于平流层和中间层中决定OH/HO2比率的反应速率系数的不确定性，或者是由于缺乏对HOx化学的充分了解。在平流层和中间层中分配OH/HO2丰度的关键反应，其速率系数近年来受到越来越多的关注，将进行研究。振动激发H2和O（3P）原子之间的反应速率系数最近被提出作为中间层中OH的新来源，将使用显式量子力学计算进行评估。测定中间层中O（3P）原子的非热能分布函数及其对O(3P)+H2碰撞中OH生成的贡献。此外，将研究由氢原子和臭氧之间的反应产生的振动激发OH的猝灭。

In this project, a number of outstanding issues related to the OH/HO2 chemistry in the upper stratosphere and lower mesophere will be investigated. Current understanding of the HOx chemistry in this region of the atmosphere is complicated because standard photochemical models or any modifications of them are unable to consistently account for the odd hydrogen abundance above and below the stratopause. This is due, in part, to uncertainties in the rate coefficients of the reactions that determine the OH/HO2 ratio in the stratosphere and mesosphere, and or due to the lack of full understanding of the HOx chemistry. The key reactions that partition the OH/HO2 abundance in the stratosphere and mesosphere whose rate coefficients have come under increased scrutiny in recent years will be investigated. Rate coefficients for the reaction between vibrationally excited H2 and O(3P) atoms which has recently been proposed as a novel source of OH in the mesosphere will be evaluated using explicit quantum mechanical calculations. Nonthermal energy distribution functions of O(3P) atoms in the mesosphere and their contributions to OH formation in O(3P)+H2 collisions will be determined. Further, quenching of vibrationally excited OH produced by the reaction between hydrogen atoms and ozone will be investigated.