Researchers at the Center for Cold Matter cooled the substance to parts per million of a degree above absolute zero. Scientists managed to set a record for approaching the lowest possible temperature. The results of the experiment have been published in the journal Nature Physics, and the study is briefly described in a press release on the Phys.org website.
Absolute zero equals minus 273.15 degrees Celsius, or 0 kelvin (K). Moreover, an increase in temperature by one degree Celsius is equal to its increase by one kelvin. The vacuum temperature exceeds absolute zero by 2.7 K due to the thermal radiation remaining after the Big Bang and uniformly filling the Universe.
In the course of numerous experiments, physicists have been able to achieve trillionths of one kelvin by cooling individual atoms, but they have not been able to do the same with molecules so far. To solve this problem, scientists combined two traditional approaches, lowering the temperature of molecules to record fractions of a degree.
The researchers used calcium fluoride molecules that were placed inside a magneto-optical trap. They were cooled using lasers. At the same time, the atoms of matter absorb radiation photons and re-emit them, losing more energy than gaining. However, in this way it is possible to lower the temperature of the molecule only to a certain limit (Doppler). To overcome this limitation, physicists applied the Sisyphean cooling method, which uses two laser beams moving towards each other, taking kinetic energy from the molecule.
The scientists stated that the temperature of the molecules cooled in this way reached 50 millionth of a degree. According to the researchers, this slows down the chemical reactions that the cooled substance enters into, allowing you to observe the mechanisms of their course.