Researchers at MIT have used lasers to bring down the temperatures of molecules to 500 nano-kelvins (about minus 273.15 Celsius), which is just 500-billionths of a degree above absolute zero. It is believed that molecules exhibit very different physical properties at such cold temperatures, and scientists have been trying to study this effect for decades. While cooling atoms has been possible earlier, this is the first time molecules (2 or more atoms chemically connected) have been cooled to this extent.
Lead Physicist Martin Zwierlein cooled down sodium-potassium gas with lasers to dissipate the energy of the individual gas molecules. The density at 500 nano-kelvins is near-zero, so it’s comparable to a vacuum state. The team then used evaporation, and then lasers to cool clouds of individual atoms. They then used a magnetic field to get them to stick together and form sodium-potassium molecules. Such molecules are not possible under normal conditions as sodium and potassium are negatively charged and hence, repel each other.
The molecule wasn’t very stable and only lasted 2.5 seconds, but the team believes that this is an important step in observing changes in quantum physics at super-cooled conditions.
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