Vibrational splittings for hydrogen atom exchange in hydroperoxo radical: the effect of oxygen-oxygen displacement and vibration

The hydroperoxyl radical, HO{sub 2}, has been the subject of numerous experimental and theoretical studies. The interest in HO{sub 2} arises primarily from its importance in combustion reactions; it is the intermediate in the reaction H+O{sub 2} {yields} O+OH, which initiates chain-branching ignition phenomena in the oxidation of H{sub 2} and most hydrocarbon fuels. Using a global potential energy surface for HO{sub 2}, the authors calculate vibrational levels up to and slightly above the energy corresponding to the potential barrier for hydrogen atom exchange for both the two-mode (excluding the O-O vibration) and three-mode (including all three vibrations) cases. They examine the vibrational splittings for hydrogen atom exchange as a function of the energy; for the two-mode calculations they consider the effect on these splittings of O-O displacement while for the three-mode calculations the effect of O-O vibration is considered.