Apparatus for cooling and trapping ultracold CaF molecules

A vacuum chamber (centre left) is part of the apparatus for trapping a dense sample of gaseous molecules. Credit: Loïc Anderegg

Atomic and molecular physics

Molecular fog cooled to 40 millionths of a degree

Laser-based technique offers means to manipulate molecular gases in new ways.

For the first time, physicists have used lasers to cool a molecular gas inside an optical trap, a system that holds matter in place with the pressure of a tightly focused laser beam.

Loïc Anderegg at Harvard University in Cambridge, Massachusetts, and his collaborators used a laser system to trap molecules of calcium–fluoride gas and then used separate lasers to chill the gas to just 40 millionths of a degree above absolute zero. This combination of methods has previously been applied only to atomic gases — those composed of atoms that are not bound into molecules.

Physicists might be able to transform super-chilled molecular gases into exotic states of matter called Bose–Einstein condensates, in which all the particles in a gas behave as if they were a single atom. Researchers might also be able to load individual ultra-cooled molecules into ‘optical tweezers’. Arrays of such tweezers could function as quantum simulators of solid materials.