Toward State-to-State Dynamics in Ultracold Collisions: Lessons from High-Resolution Spectroscopy of Weakly Bound Molecular Complexes

David J. Nesbitt shared his views on the lessons learnt from high-resolution spectroscopy of weakly bound molecular complexes regarding state-to-state dynamics in ultracold collisions. He informed that high-resolution spectroscopy permitted access to elastic, inelastic, and chemically reactive dynamics arising from pure quantum states of the complex corresponding to a snapshot of an intermolecular collision for a rigorously well-defined angular momentum state, partial wave and total parity. Observation at high spectral resolution was able project out of an ensemble and detect single quantum levels of the Hamiltonian whose dynamics was established without being described as a temperature. It was also revealed that high-resolution laser excitation out of these lower states permitted spectroscopic access to a wide range of specific internal quantum states.