Translational energy threshold for the reaction of oxygen atoms with benzene molecules

Abstract

Reactive scattering of O atoms with C₆H₆ molecules has been studied over the range of initial translational energy E= 15–35 kJ mol^–1 using a supersonic beam of O atoms seeded in an He–Ne buffer gas mixture. The total reaction cross-section was measured as a function of initial translational energy, yielding an estimated threshold energy E₀= 11 ± 3 kJ mol^–1 corresponding to a barrier in the entrance valley of the potential-energy surface. The barrier is higher than those estimated for O + C₂H₂, C₂H₄ despite these molecules having higher ionisation potentials. This accords with the spin uncoupling model of Bader et al. but not the charge transfer model of Cvetanovic.