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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., Presented at the International Symposium on Combustion (15th) held on 25-31 Aug 74 at Toshi Center Hall, Tokyo (Japan).

In principle the vibrationally excited molecular in an upper electronic state, formed by absorption in the ultraviolet region of the spectrum, can attain vibrational equilibrium by two mechanisms. In most discussions of this degradation of vibrational energy it has been considered that the data are represented adequately by a singlestep deactivation from high to low vibrational levels rather than by a multistep cascade from one group of vibrational levels to the next lower group. The present work suggests new treatments of the experimental data by which it is possible to distinguish between the single- and the multistep deactivation processes. It is demonstrated that the literature data on the quantum yield for the decomposition of hexafluoroacetone is better interpreted in terms of a multistep deactivation. Some new data are presented which support this conclusion. (Author)