Coldest Molecules on Earth Created by MIT Scientists are Colder Than Interestellar Space

Scientists have managed to create the coldest stable molecules in the world. They've cooled molecules in a gas of sodium potassium (NaK) to a temperature of 500 nanokelvins, which is just a hair above absolute zero and over a million times colder than interstellar space.

While molecules are normally full of energy, vibrating and rotating through space, the new ultracold molecules have effectively been stilled. In fact, they've been cooled to average speeds of centimeters per second and prepared in their absolutely lowest vibrational and rotational states.

"We are very close to the temperature at which quantum mechanics play a big role in the motion of molecules," said Martin Zwierlein, one of the researchers, in a news release. "So these molecules would no longer run around like billiard balls, but move as quantum mechanical matter waves. And with ultracold molecules, you can get a huge variety of different states of matter, like superfluid crystals, which are crystalline, yet feel no friction, which is totally bizarre. This has not been observed so far, but predicted. We might not be far from seeing these effects, so we're all excited."

Each molecule is composed of individual atoms that are bonded together to form a molecular structure, such as the sodium potassium molecules used in this study. The scientists used lasers and evaporative cooling to cool clouds of individual sodium and potassium atoms to near absolute zero. They then essentially glued the atoms together to form ultracold molecules, applying a magnetic field to prompt the bonding.

In order to strengthen the bond and make each molecule more stable, the researchers exposed the NaK molecules to a pair of lasers, the large frequency difference of which matched the energy difference between the molecules initial state and its lowest vibrational state.

In the end, the researchers created ultracold molecules that could pave the way to seeing exotic states of matter. To achieve this, though, the molecules will have to be cooled further to all but freeze in place.

The findings are published in the journal Physical Review Letters.

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