Ultracold, ultracool

Debbie Jin wasn’t looking for chemical reactions in 2008 when she cooled a gas of potassium and rubidium molecules to extremely cold temperatures near absolute zero.

But Jin — adjunct professor of physics at the University of Colorado-Boulder and fellow of the National Institute of Standards and Technology — couldn’t help but notice their presence.

“Nobody would have even thought about chemical reactions at those temperatures,” said Jin, who worked on the research with fellow CU faculty member Jun Ye.

The discovery has driven Jin’s study of ultracold chemistry ever since.

Earlier this year, Jin received a L’Oreal-UNESCO Women in Science award for the 2008 achievements. She was cited “for having been the first to cool down molecules so much that she can observe chemical reactions in slow motion, which may help further understanding of molecular processes which are important for medicine or new energy sources.”

Researchers had created an ultracold gas of molecules before, but Jin’s and Ye’s gas of molecules was 1,000 times colder and 1 million times denser than previous attempts.

“We’re the first to have enough that you could have almost a quantum gas,” Jin said.

Jin says the ultracold chemistry is helping to aid in simulation of the physics of quantum magnetism. Molecules have advantages over atoms in that regard, she said, because they can interact at a distance.

“Now you can have a direct interaction that … makes it easier to see magnetism and various behaviors that depend on that interaction,” she said.

Part of the reason for the work, as well, is creating an environment where everything about a chemical reaction can be controlled and to understand if chemical reactions can be turned off, which they can.

“It’s driven by trying to advance understanding,” Jin said. “It’s more about extreme control of simple systems and seeing what’s possible.”

Jin, who earned a bachelor’s degree in physics from Princeton University and a doctorate from the University of Chicago, has taught at CU since 1997. She first got into ultracold gases in the late 1990s while working for Nobel Prize winners Eric Cornell and Carl Wieman.

She was elected to the National Academy of Sciences in 2005, was named a fellow of the American Academy of Arts and Sciences in 2007 and has won several other awards.

Her current research, after getting a starting boost in 2005 by the Keck Foundation, is being funded largely by NIST, the National Science Foundation and the U.S. Air Force.

“It’s interesting just to go someplace that’s a new frontier, some place people haven’t gone before,” Jin said of her work. “It would be exciting to do something that takes a large step forward toward something people haven’t been able to do in the past.”