Master equation models for the pressure- and temperature-dependant reactions HO+NO2 → HONO2 and HO+NO2 → HOONO

Data for the reactions between OH and NO2 have been modeled using a multiwell, multichannel master equation approach. In this work, new ab initio quantum chemical results for cis-cis- and trans-perp-HOONO at the QCISD(T)/cc-pVDZ level are used with the multiple-well, multiple-channel master equation approach in order to model the data between 220 and 430 K in both He and N-2. The results are in good agreement with the experimental data over the entire ranges of temperature and pressure. The contribution from HOONO is evaluated for the experimental conditions. It is also evaluated for the conditions described by the U.S. Standard Atmosphere (1976). Although the HONO2 pathway dominates over all atmospheric conditions, up to -20% of the reaction is predicted to yield HOONO near the tropopause. If the atmospheric fate of HOONO is different than that of HONO2, this can affect atmospheric chemistry models.