A chilling effect for molecules

Molecules containing three atoms have been laser-cooled to ultracold temperatures for the first time. John Doyle and colleagues at Harvard University in the US used a technique called Sisyphus cooling to chill an ensemble of about a million strontium-monohydroxide molecules to 750 μK.

Paul S. Julienne

Adela Marian, Břetislav Friedrich

A Sisyphean task: Laser cooling of molecules is difficult, mainly due to their rich vibrational structure, typically requiring dozens of repumping lasers. However, a proof-of-principle experiment to laser cool SrF molecules has been done (see picture), showing that laser cooling of some molecules is possible with just three lasers, as Highlighted herein.

Arian Jadbabaie

James Glanz

Clouds of atoms cooled to almost absolute zero can form a collective state--in effect, a giant atom--called a Bose-Einstein condensate (BEC). The stability of a BEC depends almost entirely on how the atoms making it up interact one-on-one, and collisions of ultracold atoms provide a glimpse of these interactions. In a first-ever detection, a group of researchers in Paris has gotten cesium atoms to form ordinary molecules chilled to 300 millionths of a kelvin--something only seen before with atoms--which could be the first step toward studying complex materials in the world of the ultracold.

Heather J. Lewandowski