The rotation of a molecule, an event that lasts 125 picoseconds, has been filmed

A group of researchers has succeeded in filming the ultrafast rotation of a molecule composed of one atom of oxygen, one of carbon and one of sulfur. The short film follows a revolution and a half made by the carbonyl sulfide molecule (OCS), an event that takes place within 125 picoseconds (divide a second into a trillion parts and take 125).

The related study, published in Nature Communications, was carried out by researchers led by Jochen Küpper of the Center for Free-Electron Laser Science (CFEL) and by Arnaud Rouzée of the Max Born Institute in Berlin. The importance of the success of this project is underlined by Küpper himself who explains that it is a long time since science has been trying to capture the very fast movement of atoms, which has been impossible until now due to the need for high-energy radiation with very small wavelengths, substantially the size of an atom, in order to see the details of the event itself.

However, the research group used a different method based on two pulses of infrared laser light. The latter were tuned together and separated by 38 picoseconds to capture the carbonyl sulphide molecules that rotate very quickly in unison. With a third laser pulse, with a slightly longer wavelength, they were able to accurately determine the position of the molecules.

The result was a “database” of 651 images which entirely follow a period and a half of rotation of the molecule. The images were then attached to each other and a 125 picosecond film was obtained that follows one and a half turns of the molecule.

If you think of a rod that turns on itself you are wrong, as Küpper himself states: these are processes governed by quantum mechanics on such a small scale that it is not possible to find comparisons in objects and in everyday life in general. This also derives from the fact that the position and the moment of a molecule cannot be calculated in a precise manner simultaneously.