The textbooks do not quite have it right. There are several competing collisional mechanisms by which atoms my recombine to form molecules, and most texts assume the principal route is by two atoms colliding to form a (relatively) long-lived metastable state, which is then de-energized by a subsequent collision with another body. There is growing evidence that other mechanisms contribute significantly. In particular, we find that the direct mechanism, by which three atoms collide simultaneously to form a diatomic molecule and leave a third spectator atom, is very important in the recombination of simple atoms.
This project is carrying out accurate one- and three-dimensional quantum mechanical calculations of three-body atomic recombination and collision-induced dissociation. For some preliminary information, you can see the report (in pdf format), "Mechanisms of Recombination and Collision-Induced Dissociation," which is part of LANL Report LA-UR-97-1559.
For more recent results, see publications by the investigators in the Journal of Chemical Physics.
People in T-12 working on this project include: