New cooling technique to nanokelvin temperatures

MIT physicists have found a way to cool molecules of sodium lithium down to 220 nanokelvins, just a hair above absolute zero. They did so by applying a technique called collisional cooling, in which they immersed molecules of cold sodium lithium in a cloud of even colder sodium atoms. The ultracold atoms acted as a refrigerant to cool the molecules even further.

Collisional cooling is a standard technique used to cool down atoms using other, colder atoms. And for more than a decade, researchers have attempted to supercool a number of different molecules using collisional cooling, only to find that when molecules collided with atoms, they exchanged energy in such a way that the molecules were heated or destroyed in the process, called “bad” collisions.

In their own experiments, the MIT researchers found that if sodium lithium molecules and sodium atoms were made to spin in the same way, they could avoid self-destructing, and instead engaged in “good” collisions, where the atoms took away the molecules’ energy, in the form of heat. (SciTechDaily)

Their findings have been published in the journal Nature.

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