Kinematic slowing of molecules formed by reactive collisions

We report the generation of a beam of slow (translationally cold) KBr molecules formed by exoergic reactive collisions in counterpropagating beams of K atoms and HBr molecules. The intensity of the slow beam is estimated to 4x10(11) s(-1) sr(-1). The velocity distribution (density) peaks at 42.5 m/s corresponding to a formal temperature of 13 K. About 7% of the molecules move at velocities between 14.2 and 20 m/s and an estimated fraction of 7% is slower than 14.2 m/s.