Probing the dynamics and bottleneck of the key atmospheric SO2 oxidation reaction by the hydroxyl radical

• 成果类型: Article
• 署名作者: Yuana, Dao-Fu; Liu, Yang; Trabelsi, Tarek; Zhang, Yue-Rou; Li, Jun; Francisco, Joseph S.; Guo, Hua; Wang, Lai-Sheng
• 署名单位: Chinese Academy of Sciences; University of Science & Technology of China, CAS; Brown University; University of New Mexico; Chongqing University; University of Pennsylvania; University of Pennsylvania
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9364
• DOI: 10.1073/pnas.2314819121
• 发表日期: 2024-02-06
• 关键词: transition-state spectroscopy; reaction oh+so2; rate constants; sulfuric-acid; hoso2; photoelectron; oh; kinetics; matrix; photodetachment

摘要

SO2 (Sulfur dioxide) is the major precursor to the production of sulfuric acid (H2SO4), contributing to acid rain and atmospheric aerosols. Sulfuric acid formed from SO2 generates light- reflecting sulfate aerosol particles in the atmosphere. This property has prompted recent geoengineering proposals to inject sulfuric acid or its precursors into the Earth's atmosphere to increase the planetary albedo to counteract global warming. SO2 oxidation in the atmosphere by the hydroxyl radical HO to form HOSO2 is a key rate- limiting step in the mechanism for forming acid rain. However, the dynamics of the HO + SO2 -> HOSO2 reaction and its slow rate in the atmosphere are poorly understood to date. Herein, we use photoelectron spectroscopy of cryogenically cooled HOSO2- anion to access the neutral HOSO2 radical near the transition state of the HO + SO2 reaction. Spectroscopic and dynamic calculations are conducted on the first ab initio-based full- dimensional potential energy surface to interpret the photoelectron spectra of HOSO2- and to probe the dynamics of the HO + SO2 reaction. In addition to the finding of a unique pre-reaction complex (HO center dot center dot center dot SO2) directly connected to the transition state, dynamic calculations reveal that the accessible phase space for the HO + SO2 -> HOSO2 reaction is extremely narrow, forming a key reaction bottleneck and slowing the reaction rate in the atmosphere, despite the low reaction barrier. This study underlines the importance of understanding the full multidimensional potential energy surface to elucidate the dynamics of complex bimolecular reactions involving polyatomic reactants.