Ultracold molecules, with their extraordinary controllability, offer a host of applications in both physics and chemistry, including quantum computation and simulation, test of fundamental physics theories, precise determination of molecular constants, and state-to-state reaction dynamics. Yet, because the creation of these molecules require highly specialized techniques and fortuitous molecular properties, the number of species which can be made ultracold in labs remains very limited (and chemistry is less fun with only a few at the party!).
Here in the Liu lab, we are working to expand the chemical space of ultracold molecules using an ion-neutral hybrid platform that enables the quantum control of a variety of atoms and molecules. Our approach exploits the fact that, unlike neutral molecules, molecular ions can be cooled, trapped, and controlled using generalized techniques. Any charged molecular species may be incorporated into a Coulomb crystal of laser-cooled atomic ions of similar charge-to-mass ratio, and enjoy sympathetic cooling of their translational motion. The internal molecular motion (e.g., rotation, vibration) may be cooled via radiative thermalization to a cryogenic environment, collisions with a cold buffer gas, or, in the case of single molecular ions, quantum-logic spectroscopy. From the ultracold molecular ions, desired neutral fragments may be generated using near-threshold photodissociation, and further captured into a magnetic or optical dipole trap. This will bring many neutral species which cannot be laser-cooled into the ultracold regime.
Our new platform will enable ultracold molecule applications that advance the two pillars of physical chemistry: structure and dynamics.