A measurement made under the "wrong" experimental conditions has given physicists in Canada and China an unexpected insight into how atoms interact with each other in ultracold gases.
Scott Smale was a new PhD student in the lab of Joseph Thywissen at the University of Toronto, when he took spectroscopy data from an ensemble of trapped potassium atoms that were accidently set to interact with each other via a p-wave process, where the atoms do not collide head-on. This was a mistake because conventional wisdom holds that p-wave interactions make atoms very difficult to trap, and the ensemble would very quickly disperse before Smale saw anything. Instead, he was able to measure very distinct features of a gas dominated by p-wave interactions, which he and his colleagues then set about studying in much more detail.
"Nature surprised us," says Thywissen. "There was a beautiful spectroscopic signal of a new kind of pressure that was due to p-wave interactions."
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