The reaction of acetylperoxy and HO<sub>2</sub> radicals has a significant impact on the lower troposphere, particularly in the reaction's ability to generate OH, the most important oxidant in the troposphere. The most recent experimental measurements of OH yield do not agree with each other. Moreover, the best available statistical rate theory model requires ad hoc adjustments to the relative energy of an intermediate and a transition structure to predict reasonable branching ratios, and the model fails to reproduce the pressure dependence in experimental branching ratios. We have used Weizmann-1 Brueckner Doubles (W1BD) theory and equation-of-motion spin-flip coupled cluster (EOM-SF-CCSD(dT)) theory to recompute the energies of both singlet and triplet pathways for this reaction. W1BD relative energies for doublet, triplet, and closed-shell singlet species agree with previous CBS-QB3 results to within 1 kcal/mol. In contrast, the EOM-SF-CCSD(dT) energies for open-shell singlets disagree with previous CBS-QB3 energies by greater than 1 kcal/mol.

High-accuracy electronic structure calculations of the acetylperoxy/HO<sub>2</sub> reaction mechanism

255th National Meeting (2018)

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High-accuracy electronic structure calculations of the acetylperoxy/HO2 reaction mechanism

High-accuracy electronic structure calculations of the acetylperoxy/HO₂ reaction mechanism