Collisions Key in Creating a Quantum Degenerate Gas from Molecules

Cool a gas to a low enough temperature and it enters the so-called quantum degenerate regime, where quantum behaviors dominate. Degenerate gases consisting of fermions have long been made using fermionic atoms, but doing the same with molecules is trickier due to their complex energy structures. Last year, a team at JILA in Colorado made a degenerate Fermi gas from potassium–rubidium molecules. Now the same team explains the mechanisms that allowed them to get their gas so cold. The work provides a pathway to cooling molecular gases to even lower temperatures and deeper degeneracies. These gases could be used to study chemical dynamics in a fully quantum regime and to perform fundamental tests of quantum physics.