A group of scientists from the University Goethe of Frankfurt measured the smallest unit of time ever measured before, which represents the time it takes for a photon to travel through a molecule of hydrogen (molecular hydrogen, H ₂). It is a measure in the order of magnitude of zeptoseconds , i.e. one trillionth of a billionth of a second, and i.e. 01 ^{– 21} seconds.

Record: The smallest time interval ever measured is 247 zeptoseconds

This is a result that breaks down a previous record, achieved in 2016 and always in the zeptosecond domain: then the researchers were able to measure a time interval of 850 zeptoseconds. This time it was possible to measure a three times lower range: 247 zeptoseconds . This is a huge increase in precision over the order of magnitude of femtoseconds, equal to one millionth of a billionth of a second.

In 1999 on Egyptian chemist Ahmed Zewail received the Nobel Prize for Chemistry precisely for his works on the study of the interactions between molecules in time intervals in the order of femtoseconds, becoming a true pioneer of femtochemistry.

Schematic representation of the zeptosecond measurement. In yellow the photon that crosses the hydrogen molecule (in red the nuclei).

Goethe University researchers exploited the Deutch Elektronen-Synchroton , a particle accelerator located in Hamburg and used the X-rays of the PETRA III : X-ray energy was adjusted so that a single photon could eject two electrons from the hydrogen molecule. This interaction created an interference pattern that the researchers measured using a COLTRIMS reaction microscope, which stands for Cold Target Recoil Ion Momentum Spectroscopy.

247 zeptoseconds: is the light passing through a hydrogen molecule

This is an extremely sensitive particle detector capable of recording atomic reactions and molecular that occur very quickly. It is through this tool that the researchers were able to determine that 247 zeptoseconds is the time it takes for light to pass through the molecule.

“Since we know the spatial orientation of the hydrogen molecule, we used the interference of the two electronic waves to accurately calculate the moment when the photon reached the first and then the second hydrogen atom. And this goes up to 247 zeptoseconds, depending on how far apart the two atoms of the molecule are from the point of view of light “explained