Physicists watch 3 individual atoms collide

For the first time, physicists isolated individual atoms and dropped them together and watch them collide. What did they see?

Scientists Mikkel Andersen (left) and Marvin Weyland in their physics lab
University of Otago, New Zealand

For the first time, physicists isolated individual atoms and dropped them together and watch them collide. What did they see? They saw the formation of molecules, of course. When the three atoms approached each other, two formed a molecule. This process released energy, the effect of which was felt by all the three atoms. A microscope camera allowed the process to be magnified and viewed. 

LASER-cooled atom clouds viewed through a microscope camera
University of Otago, New Zealand

“Two atoms alone can’t form a molecule, it takes at least three to do chemistry. Our work is the first time this basic process has been studied in isolation, and it turns out that it gave several surprising results that were not expected from previous measurement in large clouds of atoms,” says Postdoctoral Researcher Marvin Weyland, who spearheaded the experiment. The results of their experiments were published in Physical Review Letters​.

“This process, known as three-body recombination, occurs everywhere from laboratory plasmas to star-forming gas clouds, but despite its ubiquity, it had yet to be directly observed, says Katherine Wright, Senior Editor for Physics Magazine. 

The physicists used laser-guided forceps called optical tweezers to pin down and hold isolated Rubidium atoms. They had to do this ultra-cold conditions (almost absolute zero degrees kelvin) and a vacuum to ensure the atoms didn’t go berserk. They then allowed the atoms to fall towards each other. They observed that two of the rubidium atoms formed a dirubidium molecule while the third one just hanged around.

“By working at this molecular level, we now know more about how atoms collide and react with one another. With development, this technique could provide a way to build and control single molecules of particular chemicals,” Weyland adds.

Associate Professor Andersen admits the technique and level of detail can be difficult to comprehend to those outside the world of quantum physics, however he believes the applications of this science will be useful in development of future quantum technologies that might impact society as much as earlier quantum technologies that enabled modern computers and the Internet.

“Research on being able to build on a smaller and smaller scale has powered much of the technological development over the past decades. For example, it is the sole reason that today’s cellphones have more computing power than the supercomputers of the 1980s. Our research tries to pave the way for being able to build at the very smallest scale possible, namely the atomic scale, and I am thrilled to see how our discoveries will influence technological advancements in the future,” Associate Professor Andersen says.

The experiment findings showed that it took much longer than expected to form a molecule compared with other experiments and theoretical calculations, which currently are insufficient to explain this phenomenon. While the researchers suggest mechanisms which may explain the discrepancy, they highlight a need for further theoretical developments in this area of experimental quantum mechanics.

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