On the stability of the elusive HO3 radical

Abstract

The dissociation of HO₃ into OH + O₂ has been studied in a systematic and consistent way using the multireference configuration interaction method. Upon extrapolation of the calculated raw energies to the complete basis set limit and using jointly with a recent realistic estimate of the zero-point vibrational energy, the energy for OO–OH bond-breaking in the trans isomer is predicted to be of D₀ = (2.4 ± 0.1) kcal mol⁻¹, where the uncertainty reflects only the one inherent to the extrapolation. The average value so obtained falls short of the commonly accepted experimental counterpart by 0.5 kcal mol⁻¹. Reasons for the deviation are advanced, as well as an estimate of the binding energy for the cis-HO₃ isomer which is predicted to have a somewhat smaller binding energy than trans-HO₃, but likewise the latter dissociates without a barrier to the same products.