TRANSITION-STATE DYNAMICS OF F-2 REACTIVE SCATTERING(BR)

Reactive scattering of F atoms with Br-2 molecules has been studied at an initial translational energy E similar to 16 kJ mol(-1) using a su personic beam of F atoms seeded in Ne buffer gas. Laboratory angular a nd velocity distributions of BrF product have been measured. They show sharp peaking in the forward direction with almost isotropic wide ang le scattering of relative intensity similar to 0.2. Approximately half the total available energy is disposed into product translation for s cattering in the forward and backward directions with slightly lower t ranslational energy for the sideways scattering. The combination of sh arp forward scattering and high product translational energy is attrib uted to early migratory trajectories in large impact parameter collisi ons whereby the F atom reacts with the more distant Br atom of the Br- 2 molecule lying in the forward hemisphere. The isotropic wide angle s cattering arises from direct trajectories in which the F atom reacts w ith the nearer Br atom of the Br-2 molecule. Migratory dynamics are pr omoted by charge transfer interaction of the form Br2+F- which stabili ses the potential energy surface in elongated isosceles triangular FBr 2 configurations as well as in slightly bent FBrBr configurations. Com parison is made with the dynamics of the F + Cl-2, I-2, and CCl3Br rea ctions.