Chemical mechanism and kinetics study on the ocimene ozonolysis reaction in atmosphere

The ocimene ozonolysis reaction is one of the most important processes for the formation of secondary organic aerosol (SOA). In this paper, molecular orbital theory has been performed for the reaction of ocimene with O3, and the detailed reaction mechanisms of active intermediates with H2O or NO are also presented. The geometry parameters and vibrational frequencies of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis set. Single-point energy calculations are carried out at the MPWB1K/6-311+G(3df,2p) level. On the basis of the quantum chemical information, the Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition state theory (CVT) with small-curvature tunneling effect (SCT) are used to calculate the rate constants over the temperature range of 200–800 K. The arrhenius formulas of rate constants with the temperature are fitted, which can provide helpful information for the model simulation study. The atmospheric lifetimes of the reaction species are estimated according to the rate constants.