Formation of ultracold molecules in chemical reactions

We demonstrate that chemical reactions in collisions of high-energy molecular beams can generally produce molecules with zero velocity in the laboratory-fixed frame. Our analysis shows that collisions of beams may simultaneously yield slow reactant molecules and slow products. The reaction products are formed in selected ro-vibrational states and scattered in a specific direction, which can be controlled by tuning the kinetic energies of the incident beams and the angle between the beams. We suggest that chemical reactions involving alkali metal dimers may be particularly suitable for producing slow molecules in crossed beams. Our calculations show that chemical reactions of polar alkali metal dimers are barrierless.