Study of Chemical Reaction Mechanisms with Molecular Beams. The Reaction of K with HBr

The reaction between K and HBr has been studied by a molecular beam technique, using as a detector a surface ionization gauge with a tungsten and a platinum alloy filament, the former sensitive to KBr as well as to K and the latter essentially to K only. The activation energy is 3.4±0.1 kcal/mole and the probability or steric factor is about 0.1. The angular distribution of the KBr suggests that collisions with the H end of the HBr are more often fruitful than other configurations. The total collision cross section for a beam of K at 504°K in HBr at 401°K is 850×10—16 cm2.