Exploration of the potential energy surfaces, prediction of atmospheric concentrations, and prediction of vibrational spectra for the HO ₂mellip;(H ₂O) _n (n = 1-2) hydrogen bonded complexes

The hydroperoxy radical (HO ₂) plays a critical role in Earth's atmospheric chemistry as a component of many important reactions. The self-reaction of hydroperoxy radicals in the gas phase is strongly affected by the presence of water vapor. In this work, we explore the potential energy surfaces of hydroperoxy radicals hydrogen bonded to one or two water molecules, and predict atmospheric concentrations and vibrational spectra of these complexes. We predict that when the HO ₂ concentration is on the order of 10 ⁸ molecules ^.cm ^-3 at 298 K, that the number of HO ₂⋯H ₂O complexes is on the order of 10 ⁷ molecules ^.cm ^-3 and the number of HO ₂⋯(H ₂O) ₂ complexes is on the order of 10 ⁶ molecules ^.cm ^-3. Using the computed abundance of HO ₂⋯H ₂O, we predict that, at 298 K, the bimolecular rate constant for HO ₂⋯H ₂O + HO ₂ is about 10 times that for HO ₂ + HO ₂.