Collision energy dependence of the reactive scattering of Br with HAt

Laboratory angle‐differential cross sections were measured for the reaction Br+HAt→HBr+At at collision energies from 4.2 to 11.7 kcal/mol. Transformation of these data into the center‐of‐mass system revealed that the mean energy in product translation is extraordinarily small, rising from 1.5±0.2 to 3.3±0.6 kcal/mol. The ratio of products scattered forward to products scattered backward is about 1.0 to 1.5 at all collision energies studied, but more detailed angular information could not be obtained. The total reaction cross section is in the range of 1.5 to 2.0 A2 from 4.2 to 8.3 kcal/mol of collision energy, and rises to 2.9±0.34 A2 at 11.7 kcal/mol. (The uncertainties cited for the cross section values represent random errors only, systematic errors contribute an additional ±15%.) These results confirm the observations made earlier at a collision energy of 5.8 kcal/mol. Phase space calculations show that for collision energies greater than about 7 kcal/mol the total reaction cross section is approachin...