LANL: Mechanism Discovered For Controlling Ultracold Chemical Reactions

The two reaction pathways (direct and looping) combine to determine the overall reaction rate for the chemical reaction. The ultracold reaction can be turned on or off depending upon whether the interference between the two pathways is constructive or destructive. Courtesy/LANL

LANL News:

  • Discovery has important technological applications

Researchers have discovered a new interference mechanism in ultracold chemical reactions, one which has important technological applications in precision measurements, sensing and quantum computing.

“Remarkable progress in cooling and trapping molecules in recent years has opened up an entirely new energy regime for studying chemical reactivity at temperatures below one micro-Kelvin,” said Brian Kendrick, of the Los Alamos National Laboratory’s Theoretical Division. “Ultracold chemistry exhibits unique quantum properties, which provides a switch for effectively turning the reaction on or off.”

Chemical reactions at ultracold temperatures have unique (quantum) properties that do not occur at normal room temperatures, causing the ultracold chemical reaction rates to be comparable to or even larger than they are at room temperature.

The discovery of a new mechanism for controlling ultracold chemical reactions is based on the interference between two reaction pathways, which contribute to the total chemical reaction rate. The pathways add up or interfere with each other, either constructively or destructively.

At ultracold temperatures, the interference between these pathways becomes dramatically enhanced, reaching the maximum or minimum possible values allowed. Scientists can use this new mechanism to switch the reaction on or off by applying external electric or magnetic fields to control whether the interference is constructive or destructive.

This new mechanism is a general property of ultracold chemical reactions and will play a crucial role in their technological applications.

The paper “The geometric phase controls ultracold chemistry” was published in Nature Communications. It is byBrian Kendrick of Los Alamos, and Jisha Hazra and Naduvalath Balakrishnan of the University of Nevada-Las Vegas.

Support for this research is from the Laboratory Directed Research and Develop program at Los Alamos, as well as the Army Research Office—Multidisciplinary University Research Initiative and the National Science Foundation.