The reaction of hydroxyl and methylperoxy radicals is not a major source of atmospheric methanol

Rebecca Caravan, Anwar Khan, Judit Zador, Leonid Sheps, Ivan Antonov, Brandon Rotavera, Krupa Ramasesha, Kendrew Au, Ming-Wei Chen, Daniel Rosch, David Osborn, Christa Fittschen, Coralie Schoemaecker, Marius Duncianu, ASma Grira, Sebastien Dusanter, Alexandre Tomas, Carl Percival, Dudley Shallcross, Craig Taatjes

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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 (ISC) 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 the 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.
Original languageEnglish
Article number4343
Number of pages9
JournalNature Communications
Volume9
DOIs
Publication statusPublished - 19 Oct 2018

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    Caravan, R., Khan, A., Zador, J., Sheps, L., Antonov, I., Rotavera, B., Ramasesha, K., Au, K., Chen, M-W., Rosch, D., Osborn, D., Fittschen, C., Schoemaecker, C., Duncianu, M., Grira, AS., Dusanter, S., Tomas, A., Percival, C., Shallcross, D., & Taatjes, C. (2018). The reaction of hydroxyl and methylperoxy radicals is not a major source of atmospheric methanol. Nature Communications, 9, [4343]. https://doi.org/10.1038/s41467-018-06716-x