We study gas-phase chemical reactions in which we aim to control all degrees of freedom of the colliding particles, including internal states, relative velocity, and relative orientation. Observing a molecular scattering event with this degree of control provides the deepest insight into chemical reactions and allows us to study some of the most fundamental concepts in chemistry.
We investigate, in particular, polyatomic chemical reactions at energies as little as 80 mK above absolute zero. We reach these low collision energies merging two neutral supersonic expansions into a single beam such that relative molecular velocities are low even if the beams are fast in the laboratory.