Abstract
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 language | English |
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Pages (from-to) | 1066-1069 |
Number of pages | 4 |
Journal | Science |
Volume | 337 |
Issue number | 6098 |
DOIs | |
Publication status | Published - 31 Aug 2012 |