Recombination of Bromine Atoms between 300 and 6000 K, Theory and Experiment,

The dissociation of Br2 in Ar was studied in the same shock tube using three different time dependent observables which were needed to measure the rate of the reaction 1 Br2 molecular absorption, 2 Br atom two-body emission and 3 density gradient change, detected by laser schlieren technique. It was found that the first observable was most useful in determination of dissociation rate constants between about 1500 and 1800 K and the second observable between about 1200 and 1700 K. Use of these two observables yielded rate constants which were in agreement with those earlier experimental data, which are likely to be most reliable. The laser schlieren technique yielded new dissociation rate constants between 2100 and 3000 K. These data were found to be consistent with the reliable emission and absorption data, as well as with the earlier flash photolysis data. In order to interpret the experimental results and to study the dynamics of the reaction, the dissociation of Br2 in Ar was studied by 3-D classical trajectory calculations at 1500, 2500, 3500, and 6000 K. In agreement with earlier trajectory studies, it was found that Br2 molecules react only if their total energy is within a few kT of dissociation limit and that metastable molecules, with total energy above the dissociation limit, are particularly reactive. The average energy, and the average angular momentum, transferred in dissociative and non-dissociative collisions were calculated as a function of total energy of Br2 molecule.