Atomic physicists at the University of Frankfurt have for the first time studied a process that is shorter than femtoseconds in magnitude. They measured the time it takes for a photon to cross a hydrogen molecule: approximately 247 zeptosegundos o miltrillonésimas of a second for the average bond length of the molecule. This is the shortest time period that has been successfully measured to date.

Scientists in Reinhard Dorner’s laboratory carried out the measurement of time in a hydrogen molecule (H2) that irradiated with X-rays from the PETRA X-ray laser sourceIII at the DESY acceleration plant in Hamburg. The researchers set the energy of the X-rays so that one photon was enough to eject both electrons from the hydrogen molecule.

Electrons behave as particles and waves simultaneously and thus the ejection of the first electron resulted in waves of electrons being thrown first at the atom of a hydrogen molecule and then at the second in rapid succession, merging waves.

Up to 247 zeptoseconds

The photon behaved here like a flat stone that slides through water twice: cuAs a wave channel meets a wave crest, the waves from the first and second contact with the water cancel each other out, resulting in what is called an interference pattern.

Scientists measured the interference pattern of the first ejected electron using the reaction microscope COLTRIMS, a device that Dörner helped develop that makes visible the processes of ultrafast reaction in atoms and molecules.

Simultaneously with the interference pattern, the COLTRIMS reaction microscope also allowed the determination of the orientation of the hydrogen moleculenot. The researchers took advantage of the fact that the second electron also left the hydrogen molecule, so that the remaining hydrogen nuclei separated and were detected.

“Since we knew the spatial orientation of the hydrogen molecule, we used the interference of the two electron waves to calculate precisely when the photon reached the first and when it reached the second hydrogen atom“explains Sven Grundmann, whose doctoral thesis forms the basis of the scientific article published in Science. “And this is up to 247 zeptoseconds, depending on how far apart the two atoms are in the molecule from the perspective of light. “

Professor Reinhard Dörner adds: “We observed for the first time that the electron shell of a molecule does not react to light everywhere at the same time. The delay occurs because the information inside the molecule it only propagates at the speed of light. With this finding we have extended our COLTRIMS technology to another application. “