Interception of Excited Vibrational Quantum States by O-2 in Atmospheric Association Reactions

David R. Glowacki, James Lockhart, Mark A. Blitz, Stephen J. Klippenstein, Michael J. Pilling, Struan H. Robertson, Paul W. Seakins

Research output: Contribution to journalArticle (Academic Journal)peer-review

88 Citations (Scopus)


Bimolecular reactions in Earth's atmosphere are generally assumed to proceed between reactants whose internal quantum states are fully thermally relaxed. Here, we highlight a dramatic role for vibrationally excited bimolecular reactants in the oxidation of acetylene. The reaction proceeds by preliminary adduct formation between the alkyne and OH radical, with subsequent O-2 addition. Using a detailed theoretical model, we show that the product-branching ratio is determined by the excited vibrational quantum-state distribution of the adduct at the moment it reacts with O-2. Experimentally, we found that under the simulated atmospheric conditions O-2 intercepts similar to 25% of the excited adducts before their vibrational quantum states have fully relaxed. Analogous interception of excited-state radicals by O-2 is likely common to a range of atmospheric reactions that proceed through peroxy complexes.

Original languageEnglish
Pages (from-to)1066-1069
Number of pages4
Issue number6098
Publication statusPublished - 31 Aug 2012


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