Everything that happens at the level of molecules and atoms happens so fast that it is impossible to see without the use of superhigh-speed lasers or other techniques. What happens during chemical reactions also falls into this category, but scientists at Harvard University managed to produce the “coldest” chemical reaction by cooling molecules to small fractions of a degree above absolute zero. And this allowed them to see and film something that no one had ever seen before – the process of exchanging atoms between molecules.
Absolute zero (-273.15 degrees Celsius, 0 Kelvin) is considered the coldest possible temperature at which all the movement of atoms and molecules stops completely and there is no “grain” of thermal energy in these molecules and atoms. In their research, Harvard scientists cooled molecules to millionths of a degree above absolute zero, to 500 nanoKelvin, to be precise. This temperature is below any temperature of natural origin, in the coldest regions of interstellar space, the temperature is kept at 3 Kelvin.
Such a low temperature was created in the Cold Atom Lab experiment chamber, located on board the International Space Station (ISS), which is designed to conduct experiments at temperatures of about 100 nanoKelvin. In this case, a “gas”, which includes potassium and rubidium atoms, was cooled to such a low temperature. When molecules of such a gas collide, they exchange one atom, which leads to the appearance of two new molecules, one with two potassium atoms and the second with two rubidium atoms.
Under ordinary conditions, such reactions proceed very quickly, the scientists were only able to note the fact of the disappearance of two original molecules and the appearance of two new molecules. What is happening between these two stages remained a mystery until recently. However, cooling to an ultralow temperature allowed to slow down this reaction millions of times, which, in turn, made it possible to consider and capture everything that was happening.
It turns out that in the collision of two molecules of rubidium-potassium, one intermediate molecule is formed, consisting of two rubidium atoms and two potassium atoms. After that, scientists were able to see how atomic bonds in this molecule “break” and it takes on a new form, eventually dividing into two new independent molecules.
Researchers believe that such an approach will allow them to study the mechanics of chemical reactions in even greater detail in the future. Moreover, the technology of low-temperature deceleration will allow such reactions that cannot be carried out under normal conditions and even at higher, but still very low temperatures. This, in turn, will allow us to synthesize new drugs, new materials for electronics, quantum technologies and many other useful things.