TRANSITION-STATE DYNAMICS OF F+CL2 REACTIVE SCATTERING

Reactive scattering of F atoms with Cl2 molecules has been studied at an initial translational energy E almost-equal-to 16 kJ mol-1 using a supersonic beam of F atoms seeded in Ne buffer gas generated by a high -pressure microwave discharge source. The centre-of-mass angular distr ibution peaks sharply in the forward direction with a minor peak of re lative height ca. 0.2 in the backward direction. A major fraction f(pk )' almost-equal-to 0.6 of the total available energy is disposed into product translational energy for the forward and backward scattering b ut only a minor fraction f(pk)' almost-equal-to 0.16 for the sideways scattering. The total flux scattered in the sideways direction has a v ery low intensity ca. 0.06 relative to the forward scattering. The obs erved reactive scattering is related to the dynamical motion of a slig htly bent FCICl reactant transition state formed at the top of a low b arrier in the entrance valley of the potential-energy surface and its dissociation over a weakly attractive surface to form reaction product s. Transition states formed in large impact parameter collisions with the Cl2 molecule lying initially in the broadside orientation precess into the forward hemisphere and tend to dissociate adiabatically to fo rm ClF products in the ground and first excited vibrational states. Tr ansition states formed in small impact parameter collisions where the F atom interacts with the Cl atom of the Cl2 molecule lying in the bac kward hemisphere undergo dissociation from more contracted configurati ons and may form ClF reaction products in the second excited vibration al state.