The reaction of hydroxyl and methylperoxy radicals is not a major source of atmospheric methanol.
basic_science · Level V
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- Record sourced from PubMed, PMID 30341291.
- Also identified by DOI 10.1038/s41467-018-06716-x and PMC identifier 6195545.
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Abstract
Methanol is a benchmark for understanding tropospheric oxidation, but is underpredicted by up to 100% in atmospheric models. Recent work has suggested this discrepancy can be reconciled by the rapid reaction of hydroxyl and methylperoxy radicals with a methanol branching fraction of 30%. However, for fractions below 15%, methanol underprediction is exacerbated. Theoretical investigations of this reaction are challenging because of intersystem crossing between singlet and triplet surfaces - ∼45% of reaction products are obtained via intersystem crossing of a pre-product complex - which demands experimental determinations of product branching. Here we report direct measurements of methanol from this reaction. A branching fraction below 15% is established, consequently highlighting a large gap in the understanding of global methanol sources. These results support the recent high-level theoretical work and substantially reduce its uncertainties.