A group of physicists from the United States cooled molecules sodium-lithium to a temperature of 220 nanokelvin due to collisions with ultracold sodium atoms. Work published in the journal Nature.
Evaporative cooling is used to lower the temperature of our body when we sweat and cooling and appliances. The nature of this phenomenon lies in the fact that hot particles cooled systems are faced with the particles of the cooler, giving them their momentum and the latter, in turn, leave the system.
In atomic physics, evaporative cooling is used to reduce the oscillation energy of the ensemble of atoms. The technology uses an electromagnetic field to trap the atoms in the optical trap. Over time, the atoms collide with each other and some of them become more mobile than
other. Such high-energy atoms leave the trap, thereby lowering the energy of the entire system and reducing
the temperature of the remaining atoms.
Cooled quantum system can be used as a simulator of different systems of physics condensed matter or nuclear physics. However, individual atoms are too few degrees of freedom, which limits the possibilities of the simulator. Over the last 15 years, we made some serious progress in cooling more complex objects such as molecules, but, unfortunately, the achieved temperature was limited to still dozens of millikelvins.
Physics from the Massachusetts Institute of technology and Harvard University under the supervision of Professor Allan Jamieson (Alan Jamison) for the first time managed to cool the ensemble of molecules due to the evaporative cooling to a temperature of 220 nanokelvin. To do this, scientists placed 30 thousand molecules NaLi and 100 of thousands of sodium atoms in an optical trapin which the particles resist the electromagnetic field.