Reactive scattering of a supersonic oxygen atom beam O + I₂

Abstract

Reactive scattering of O atoms with I₂ molecules has been studied at an initial translational energy E = 43 kJ mol^-1 using a supersonic beam of O atoms seeded in He and E = 18 kJ mol^-1 using O atoms seeded in Ne. Velocity distributions of OI product were measured by cross-correlation time-of-flight analysis. Full contour maps of the differential reaction cross section were obtained which show predominantly rebound scattering at both initial translational energies. Scattering in the forward direction has a product translational energy distribution similar to that predicted for a long-lived collision complex but scattering in the backward direction has a much higher product translational energy. The greater predominance of rebound scattering observed for O + I₂ compared with O + Br₂ may be attributed to the greater exoergicity of the O + I₂ reaction. However, comparison with the O + IBr reaction which exhibits a long-lived collision complex mechanism indicates that the predominance of backward scattering for O + I₂ also arises from diminished forward scattering from larger impact parameter collisions.