Energy-rich collision intermediate

As noted in Section 3.1, the termolecular reaction A + B + M — AB + M does not take place as the result of the simultaneous collision of A, B, and M rather, A and B react to form an energy-rich intermediate AB1 that subsequently collides with a third molecule M (the reaction chaperone), which removes the excess energy and allows formation of AB. (The dagger denotes vibrational excitation.)... 

It can readily be seen why an energy-rich intermediate species must participate. In the dissociation direction, reaction can only occur after the molecule AB has accumulated, through collisions, enough energy to rupture the chemical bond holding A and B together in the recombination direction, the first species formed in an A-B encounter retains all of the energy of the newly formed bond until later events, i.e., subsequent collisions, cause it to be dissipated to the environment. 

At the time of the conference the study of nuclear reactions produced by intermediate energy protons or pions as well as the investigation of collisions between two nuclei of Z 2= 3 were still in a rather primitive stage whereas today they constitute a rich field of empirical knowledge and phenomenological interpretation. 

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