Reactive scattering of a supersonic oxygen atom beam : O + Cl₂

Abstract

Reactive scattering of O atoms with Cl₂ molecules has been studied at an initial translational energy E = 31 kJ mol^-1 using a supersonic beam of O atoms seeded in He and at E = 13 kJ mol^-1 using O atoms seeded in Ne. Velocity distributions of OCl product were measured by cross-correlation time-of-flight analysis. A full contour map of the differential reaction cross-section was obtained with O atoms seeded in He which peaks strongly in the forward direction with a smaller backward peak of relative height 0·30±0·1. For O atoms seeded in Ne, the relative height of the backward peak increases to 0·55±0·15. The product translational energy for scattering in the forward direction is higher than that for wide angle scattering by a factor of ∼3. Thus the O + Cl₂ reaction proceeds via a short-lived collision complex where the lifetime of the complex depends upon the initial translational energy. However, all reactive collisions do not sample the most stable configuration of the complex to an equal extent. The observed reaction dynamics indicate that reaction occurs in collisions at fairly large impact parameters b_m of ∼1·5 - 4·5 Å with a strong orientation requirement for reaction.