JILA's efforts to create and investigate cold molecules build on the Institute's ultracold atom expertise. Researchers use tools such as Feshbach resonances, laser cooling, and Stark deceleration to produce cold diatomic molecules. They study these molecules under rigorously controlled conditions, seeking to understand how to produce them in specific quantum states, track the flow of energy among molecular constituents, and control chemical reactions.

Heather Lewandowski's group uses a two-step process to prepare ultracold molecules of NH, a simple free radical that is important in the chemistry of Earth's atmosphere. First, NH molecules are forced through a small opening into a vacuum system where intermolecular collisions cool the rapidly expanding gas (700 m/s) to less than 1 K. Next, the Lewandowski group uses time-varying electric fields (Stark deceleration) to slow the cold molecules to rest. Once the molecules are cold and stopped, they are subjected to magnetic trapping, electrostatic trapping, laser cooling, or sympathetic cooling. Lewandowski is working with theorist John Bohn to investigate collisions of cold polar NH radicals (produced in this process) with each other and other ultracold atoms such as rubidium.

Jun Ye's group investigates ultracold ground-state polar molecules. His group has obtained cold samples of ground-state hydroxyl (OH) free radicals and formaldehyde (H₂CO) molecules, which are both expected to exhibit novel collision properties. These systems should bring new opportunities for control over intermolecular interactions at ultracold temperatures. The group is currently working on using optical fields to further reduce the kinetic energy of the OH radicals, with a goal of reducing the OH temperature from 15 mK to 100 μK or lower. The researchers have also begun to explore the collision dynamics between OH radicals to test theoretical predictions made by John Bohn, who also collaborates with Heather Lewandowski on the chemistry of ultracold NH radicals.

Ye's efforts to develop ultraprecise optical measurement tools has fostered a collaboration with Eric Cornell and John Bohn. Cornell is leading an effort to measure the electric dipole moment of an electron (eEDM) in trapped molecular ions. The proposed experiment will test the fundamental symmetry of nature. If an eEDM can be detected and measured, the discovery will prove that, even at the quantum level, running time forward or backward makes a difference in the behavior of individual particles.

Ultracold atom gurus Deborah Jin and Carl Wieman are teaming up with Ye to use a combination of Feshbach resonances and optical fields (created with a high-finesse optical cavity) to create a variety of ultracold molecules in different quantum states. This high-powered collaboration will employ a new apparatus (currently under construction) that uses both magneto-optical traps and evaporative cooling. The device will produce an ultracold mixture of atomic gases that can be used for cold molecule production. Experiments will start with the production of polar potassium-rubidium (KRb) molecules by applying a magnetic field across a Feshbach resonance to a mixture of ultracold atomic gases in an optical trap. Eventually, the researchers plan to combine the creation of polar molecules with optical lattice investigations.