PORTLAND, Ore. — Researchers have been able to stop and start chemical reactions between molecules at temperatures colder than the depths of outer space. And new theoretical descriptions help explain the quantum mechanical details of these ultracold chemical reactions.
The details, presented March 17 at a meeting of the American Physical Society, offer glimpses into the burgeoning field of ultracold physics, which enables the creation of strange new states of matter and has potential applications in quantum computers and precision measurement devices (SN: 12/20/08, p. 22). At temperatures this low, the molecules no longer obey everyday rules, but instead are governed by quantum mechanics.
Deborah Jin and Jun Ye, both of the University of Colorado at Boulder and the JILA research center in Boulder, led experiments which used precisely tuned lasers and electric fields to deftly start and stop reactions between ultracold potassium-rubidium molecules.
“It’s a beautiful demonstration of how quantum mechanics works,” said Jeremy Hutson, a chemist at the University of Durham in England who studies ultracold reactions. The new studies reveal the existence of strange quantum effects “in a very simple regime that’s never been explored before.”
The University of Colorado researchers used lasers to cool the potassium-rubidium molecules, halting all the frenetic motion that usually characterizes the jittery molecules. Held in this chilly “ground state” at around 200 nanokelvin, the molecules moved incredibly slowly, Ye said. But after a second or so, the molecules started to disappear by twos.
“What’s going on here is chemistry,” Jin says. The potassium-rubidium molecules interact with each other to form molecules made up of two potassium atoms and two rubidium atoms. These results also appeared February 12 in Science.