Understanding the structure and dynamics of molecules is a central mission of molecular science. The most detailed understanding - particularly that at the quantum mechanical level - often comes from studies of isolated molecules in the gas-phase. In the fields of gas-phase molecular spectroscopy and reaction dynamics, advances in our understanding of structural and dynamical details are in lock step with developments in techniques to control molecules and their interactions in the laboratory. Since the pioneering crossed molecular beam experiments of Hersbach and Lee, remarkable progress has been made in achieving increasingly finer control over both the internal quantum states (e.g., vibration, rotation, hyperfine, etc.) and the translational motion of molecules. Contributions to this progress come from both the continued refinement of the molecular beam technique, as well as the more recent developments in the field of ultracold molecules. Using molecules in well-defined quantum states and nearly at rest, experiments have achieved 10 (-14) level frequency accuracy in vibrational spectroscopy, and single quantum state resolution of both reactants and products in a bimolecular reaction.

To fully understand the results (e.g., spectrum, state-to-state reaction cross sections) from these detailed experiments, however, requires commensurate developments in theory - both electronic structures and nuclear dynamics. The electronic structure calculations yield the necessary interaction potentials on which the nuclear motions evolve. Because of the sensitivity of collisional outcome to minute details of the interaction potential ab initio quantum chemistry calculations are also put to high levels of scrutiny even for simple systems involving 3 and 4 atoms. Nuclear dynamics is equally challenging due to the large de Broglie wavelengths involved in cold collisions and the need to include the effect of external trapping fields. Recent studies have also revealed the importance of coupling to excited electronic states that are accessible in cold collisions involving alkali metal dimers - workhorse molecules for quantum science applications. Such non-adiabatic effects can lead to new quantum interference mechanisms that can enhance or suppress reaction outcomes, essentially acting as a quantum switch for chemical reactivity.

The proposed workshop aims to bring together an international group of researchers, both theorists and experimentalists, from the fields of molecular spectroscopy and reaction dynamics, to discuss the latest developments in the emerging field of cold molecules and cold chemistry, and to chart its course for the next ten years.