The coldest chemical reaction in the entire universe

How do atoms behave when they react to very low temperatures? This is the question answered by scientists from Harvard University , who managed to trigger the coldest chemical reaction in the entire universe .

Ok, cold chemical reaction … but how cold?

The reaction occurred at around 500 nanokelvin , just a few millionths of a degree above absolute zero. It is precisely the extremely low temperature that makes the team’s work even more interesting and curious: the thermal condition reached, in fact, causes a slowdown of the molecules , until they almost stop.

The ” almost ” is a must: the theoretically lowest temperature in the Universe is absolute zero (0 K), but it is impossible to achieve as this would require  completely stationary atoms  .

Furthermore, the researchers were able to observe a phenomenon never seen before: the exact moment in which two molecules react to form two new molecules. According to the physicist Ming-Guang Hu :


In the next two years, we will probably be the only laboratory capable of doing this.

Slow down the reaction to observe it closely

Chemical reactions require extremely short times , generally a few picoseconds ( 10-12 seconds), and it is very difficult, even with innovative laser instruments, to capture what happens in that time interval.

Observe what happens during a chemical reaction. Now you can. (credits: Ming-Guang Hu)

The most suitable solution was to observe the reaction “in slow motion” and the only way to do it was to trigger it at very low temperatures. Chemical biologist  Kang-Kuen Ni , also a member of the research team, explained:


Since the molecules are so cold, we have a bottleneck effect.

Ultra low temperatures imply ultra low energies which, in turn, involve much slower reactions: by using two rubidium molecules , the researchers managed to delay the reaction by a few microseconds , an objectively small but remarkably large amount of time, when compared to normal reaction times. The technique used to observe what happens while the molecules react is called  photoionization detection .

The milestone reached by Harvard scientists could be an important starting point  for future research as it would allow, for example, the design of new chemical reactions , which would potentially be useful and applicable in various sectors.

The team’s next commitments concern the study of ways in which to influence or manipulate reactions , for example by varying the energies involved. Ming-Guang Hu also said so, saying:

Now we can think about how to influence reactions. Without this technique, without this document, we could not have even imagined it.


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