Tweezers made of laser beams manipulate atoms to make new molecules

By Dr. Ananya Mandal, MDApr 13 2018

Researchers have devised optical tweezers made up of laser beams that could be used to manipulate and move tiny atoms to align them to form single molecules. This is a breakthrough and has been done for the first time by scientists from Harvard University. The work report was published in a study in the latest issue of the journal Science.

According to the researchers, this is the first time a device has been made that could make designer molecules which are built like building blocks – one atom at a time. Until now making molecules meant putting atoms or molecules in close proximity and hoping that they would react with each other by colliding. The final outcome of such random pairings would then be analysed to see if the desired molecule is created. This laser tool now can make molecules perfectly and as per need.

For this study the team got hold of two single atoms - sodium and cesium using two different optical tweezers or beams and brought them close to create a single molecule of sodium cesium (NaCs). Molecules created in this manner can be highly selective and precise. More diverse and complex molecules that are to be used for quantum information applications and quantum computing can also be synthesized using this technique say researchers.

Lee Liu - a PhD student at Harvard University, and colleagues in this study thus worked with just two atoms. Both the atoms were laser-cooled to absolute zero, or minus 273 degrees Celsius. This was because any warmer and the atoms would be moving around too much to be caught in the beams. The atoms were moving about when the laser beams with their small packets of energy called photons were used to stop them in a place. The wavelengths of the two laser beams that carried the atoms were different. One atom of sodium and cesium were then caught from the ultraclod cloud the researchers explain. The different wavelengths of the beams ensured that they would be specific for each of the atoms. The final NaCs molecule that they created was in an excited state they said. The team looked at this new molecule using spectroscopy and found that it had some unique properties that were not known before.

Liu said, “Every high school student of chemistry, looking at a textbook, sees 'A plus B equals AB'… For the first time, we've been able to do this in the lab.”