On the stability of the elusive HO3 radical

The dissociation of HO(3) into OH + O(2) 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 D(0) = (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-HO(3) isomer which is predicted to have a somewhat smaller binding energy than trans-HO(3), but likewise the latter dissociates without a barrier to the same products.