Ab initio rate coefficients for the reaction of OH and H2O2 under upper troposphere and lower stratosphere conditions

Abstract

The reaction between hydrogen peroxide (H₂O₂) and hydroxyl radical (OH) plays an important role in the upper troposphere and lower stratosphere (UTLS). However, direct experimental studies are lacking for this UTLS regime for a temperature range of 190–250 K. In this work, mechanism and kinetics for the title reaction were studied using high-level theoretical methods to provide highly accurate rate coefficients for the UTLS regime. The reaction was found to proceed via a van der Waals (vdW) complex at low temperatures, but to undergo a direct H-abstraction via a well-skipping mechanism at higher temperature to yield products HO₂ + H₂O. The ab initio rate coefficients are pressure-independent under terrestrial atmospheric conditions (T = 180–350 K and P ≤ 1 atm) and agree well to within 20% with most experimental data available for T = 165–500 K.