Thermal and Vibrationally Activated Decomposition of the syn-CH$_3$CHOO Criegee Intermediate

TL;DR

This study investigates the decomposition pathways of the syn-CH$_3$CHOO Criegee Intermediate, revealing how vibrational excitation influences reaction rates and atmospheric OH production, with implications for atmospheric chemistry modeling.

Contribution

It provides a detailed reaction pathway analysis and compares vibrationally excited and thermal reactants, highlighting the role of vibrational energy in reaction dynamics.

Findings

Vibrational excitation rates match experimental data.

Tunneling is not necessary for reactivity.

Vibrationally excited reactant accumulates, affecting OH production by nearly an order of magnitude.

Abstract

The full reaction pathway between the syn-CH$_3$CHOO Criegee Intermediate via vinyl hydroxyperoxide to OH+CH$_2$COH is followed for vibrationally excited and thermally prepared reactants. The rates from vibrational excitation are consistent with those found from experiments and tunneling is not required for reactivity at all initial conditions probed. For vibrationally excited reactant, VHP accumulates and becomes a bottleneck for the reaction. The two preparations - relevant for laboratory studies and conditions in the atmosphere - lead to a difference of close to one order of magnitude in OH production (~ 5 % vs. 35 %) on the 1 ns time scale which is an important determinant for the chemical evolution of the atmosphere.