Product-state control of bi-alkali-metal chemical reactions

We consider ultracold, chemically reactive scattering collisions of the diatomic molecules KRb. When two such molecules collide in an ultracold gas, we find that they are energetically forbidden from reacting to form the trimer species K2Rb or Rb2K, and hence can only react via the bond-swapping reaction 2KRb→K2+Rb2. Moreover, the tiny energy released in this reaction can in principle be set to zero by applying electric or microwave fields, implying a means of controlling the available reaction channels in a chemical reaction.