The behavior of small molecules, alone and in reactions with one another, has been well studied. The basic physics is simple to describe: To a good approximation, it’s just nonrelativistic quantum mechanics with Coulomb interactions. Exact solutions to the Schrödinger equation are not feasible for any but the simplest systems; as a result, many quantitative details—reaction rates, cross sections, energy barriers, and the like—remain to be measured or numerically determined. And there’s plenty of room for innovative new computational and experimental techniques to illuminate those details (see, for example, Physics Today, October 2013, page 15, and November 2013, page 15).
By and large, though, molecules’ dynamics are consistent with the patterns established by generations of experiments and calculations that have come before. It’s highly unusual for a pair of colliding molecules to behave in a way that’s qualitatively new and unexpected. But in an experiment by the...
