Reactive scattering of a supersonic chlorine atom beam Cl + I2

Reactive scattering of Cl atoms with I2 molecules has been studied at an initial translational energy E = 61 kJ mol-1 using a supersonic beam of Cl atoms seeded in He and at E = 26 kJ mol-1 using Cl atoms seeded in Ne. Velocity distributions of ICl product were measured by cross-correlation time-of-flight analysis. Full contour maps of the differential reaction cross section have been obtained which show sharp peaking in the forward direction at both initial translational energies. The product translational energy distributions are independent of scattering angle and show that a substantial fraction f′pk ∼ 0·35, f′av ∼ 0·5 of the total available energy is disposed into translation. These results are interpreted in terms of the stripping model due to Herschbach, which identifies two components in the reactive scattering; wide angle scattering arising from smaller impact parameter collisions and forward scattering arising from a narrow range of the largest impact parameters. The transition state for forward scattering involves a nearly collinear configuration lying in the plane of the collision.