The physicists created a microwave refrigerator for molecules and set a cooling record

The physicists created a microwave refrigerator for molecules and set a cooling record

Physicians used a rotating microwave field to cool a gas consisting of polar molecules to record low temperatures, and this technology will help to better understand the quantum state of matter and its properties.

For their experiments, researchers used a gas consisting of sodium and potassium molecules, which were held in an optical trap by laser radiation.

The principle of this method is based on the collision of particles in a magnetic trap. Individual atoms, when confronted with each other, transmit part of their kinetic energy. With the passage of time, individual atoms become much more powerful than others, leaving the trap, reducing the energy of the system and the temperature of the group of atoms remaining in it.

The polar molecules are characterized by an uneven distribution of electrical charge, explained by scientists. Unlike free atoms, they can rotate, vibrate, attract, or pull away from each other. They behave like tiny magnets and can stick together to prevent cooling.

To eliminate this limitation, researchers used a specially designed electromagnetic field, which serves as an energy shield for molecules and prevents them from clinging and sticking. Under the influence of the field, if two molecules come too close to each other, they can exchange kinetic energy, but at the same time they are structured in such a way that they push each other away and move quickly in different directions.

To create a microwave field with the required properties, researchers placed a spiral antenna under an optical trap containing gas from sodium-calium molecules, and in this experimental installation the molecules have been encountered much more frequently, on average about 500 times on the molecule.

As a result, only one third of a second later, the temperature reached about 21 nC, well below the critical Fermi temperature, below which quantum effects determine the behaviour of the gas.

Researchers believe that the new refrigeration technology will allow the creation and study of various quantum forms of matter that were previously predicted in theory.