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Yuan DF, Liu Y, Trabelsi T, Zhang YR, Li J, Francisco JS, Guo H, Wang LS. Probing the dynamics and bottleneck of the key atmospheric SO 2 oxidation reaction by the hydroxyl radical. Proc Natl Acad Sci U S A 2024; 121:e2314819121. [PMID: 38285944 PMCID: PMC10861908 DOI: 10.1073/pnas.2314819121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 12/29/2023] [Indexed: 01/31/2024] Open
Abstract
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⋯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.
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Affiliation(s)
- Dao-Fu Yuan
- Hefei National Research Center for Physical Science at Microscale, University of Science and Technology of China, Hefei230026, China
- Department of Chemistry, Brown University, Providence, RI02912
| | - Yang Liu
- School of Chemistry and Chemical Engineering, Chongqing University, Chongqing401331, China
- Department of Chemistry and Chemical Biology, Center for Computational Chemistry, University of New Mexico, Albuquerque, NM87131
| | - Tarek Trabelsi
- Department of Earth and Environmental Sciences, University of Pennsylvania, Philadelphia, PA19104
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA19104
| | - Yue-Rou Zhang
- Department of Chemistry, Brown University, Providence, RI02912
| | - Jun Li
- School of Chemistry and Chemical Engineering, Chongqing University, Chongqing401331, China
| | - Joseph S. Francisco
- Department of Earth and Environmental Sciences, University of Pennsylvania, Philadelphia, PA19104
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA19104
| | - Hua Guo
- Department of Chemistry and Chemical Biology, Center for Computational Chemistry, University of New Mexico, Albuquerque, NM87131
| | - Lai-Sheng Wang
- Department of Chemistry, Brown University, Providence, RI02912
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Keshavarz F. Chemical Kinetics Approves the Occurrence of C ( 3P j) Reaction with H 2O. J Phys Chem A 2019; 123:5877-5892. [PMID: 31268710 DOI: 10.1021/acs.jpca.9b03492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although both atomic carbon and water are omnipresent in human life, there is a debate about the possibility of carbon reaction with water. Some low-temperature spectroscopic investigations have rejected the reaction, whereas some room-temperature experiments and theoretical studies have accepted the possibility of the reaction by reporting rate coefficients ranging from 105 to 109 L mol-1 s-1. This study provides new lines of evidence about the reaction through exploration of the reaction mechanism using the CCSD(T) method and solving the corresponding master equation by following two main approaches. According to the results, the rate coefficient of the reaction is significantly influenced by the tunneling and hindered rotation effects, in addition to the selected total angular momentum (J). Furthermore, the total rate coefficient of the reaction increases dramatically (from 107 to 1011 L mol-1 s-1) with the rise of temperature from 100 to 4000 K, while the total rate coefficient is insensitive to pressure (0.1-10 atm). Despite some differences between the results of the two approaches, the rate coefficients of both methods are consistent with the previously reported rate coefficients. Also, in agreement with the previous studies, the major products are 2HOC + 2H and 2HCO + 2H. In general, the findings approve the occurrence of the title reaction and indicate that the mentioned conflict is due to the sensitivity of the reaction to the investigated temperature and J level. The sensitivity does not permit low-temperature spectroscopic studies to detect any products and varies the measured and calculated rate coefficients.
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Affiliation(s)
- Fatemeh Keshavarz
- Department of Chemistry, College of Science , Shiraz University , Shiraz 71946-84795 , Iran
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Lockhart JPA, Gross EC, Sears TJ, Hall GE. Kinetic study of the OH + ethylene reaction using frequency‐modulated laser absorption spectroscopy. INT J CHEM KINET 2019. [DOI: 10.1002/kin.21265] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | - Eisen C. Gross
- Department of ChemistryStony Brook University Stony Brook New York
| | - Trevor J. Sears
- Division of Chemistry, Brookhaven National Laboratory Upton New York
- Department of ChemistryStony Brook University Stony Brook New York
| | - Gregory E. Hall
- Division of Chemistry, Brookhaven National Laboratory Upton New York
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