Molecular Beam Kinetics: Differential Cross Sections of the Reactions Cl+I2 and Cl+IBr

The chemical reactions $\mathrm{Cl}+{\mathrm{I}}_2$ and $\mathrm{Cl}+\mathrm{IBr}$ were studied using a crossed molecular beam apparatus. Angular and recoil velocity distributions were obtained for all reaction product molecules. In the center of mass system the forward to backward scattering ratios for the reactions $\mathrm{Cl}+\mathrm{IBr}\mathrm{,\hspace{0.17em}}\mathrm{Cl}+{\mathrm{I}}_2\mathrm{,\hspace{0.17em}}\mathrm{Cl}+{\mathrm{Br}}_2$ , [N. Blais and J. Cross, J. Chem. Phys. 52, 3580 (1970)] and $\mathrm{Cl}+\mathrm{BrI}$ were found to be 4, 6, 8, and 12, respectively. The recoil energy distributions were determined by the chemical bond being formed rather than the one which was broken. For ICl, 50% of the total available energy was found in internal excitation with a very broad distribution. For BrCl, 80% of the total available energy was found in internal excitation with a rather narrow distribution. We conclude that the angular distributions are consistent with those arising from short range attractive forces and that the reaction time is less than one rotational period.