Reactive scattering of hydroxyl radicals : OH + Br₂

Abstract

Angular and velocity distribution measurements of HOBr reactive scattering from crossed beams of OH radicals and Br₂ molecules are reported. The OH radical beam was generated by the reaction of H atoms, formed in a microwave discharge through a low pressure flow of H₂, with NO₂ gas in a pyrex mixing source. The Br₂ beam was generated from a supersonic nozzle source at ∼400 K with a stagnation pressure ∼100 Torr. Product velocity distributions were measured at each laboratory scattering angle by the cross-correlation time-of-flight method. The scattering data are found to be in good agreement with the RRKM-AM model of reactive scattering via a long-lived collision complex, with similar parameters to the O + Br₂, I₂ reactions. This indicates the existence of an HOBrBr collision complex, whose stability and possible structure are rationalized in terms of Walsh molecular orbital theory.