Physicists from Frankfurt, Hamburg and Berlin monitor the spread of light in a molecule.
In the global race to measure shorter time, physicists from Goethe University Frankfurt took the lead: along with colleagues at the accelerator facility DESY at Hamburg and the Fritz-Haber-Institute in Berlin, they measured a process that lies within the field of zeptoseconds for the first time: the propagation of light within a molecule. A zeptosecond is a trillion percent of a second (10)-21 seconds).
In 1999, Egyptian chemist Ahmed Zewail received the Nobel Prize for speed measurement in which molecules change their shape. He established femtochemistry using ultrashort laser flashes: the formation and breakdown of chemical bonds occurs in the field of femtoseconds. A femtosecond equals 0.000000000000001 seconds, or 10-15 seconds
Now the atomic physicists at Goethe University on the team of Professor Reinhard Dörner are at first studying a process shorter than the femtoseconds of force. They measured how long it took for a photon to cross a hydrogen molecule: about 247 zeptoseconds for the average molecular bond length. This is the shortest amount of time that has been successfully measured so far.
Scientists are performing a time measurement on a hydrogen molecule (H2) that they X-rayed from the PETRA III synchrotron lightsource at the Hamburg accelerator center DESY. The researchers set the X-ray energy so that one photon was sufficient to release both electrons from the hydrogen molecule.
Electrons act like particles and waves simultaneously, and therefore the emission of the first electron results in electron waves being launched first in one, and then in the second hydrogen molecule. atomo in rapid order, in waves integration.
The photon acts here like a flat pebble that is skimmed twice across the water: when a wave in the trough meets a vertex, the waves of the first and second contact with water canceled each other, resulting in a so-called pattern of disruption.
Scientists measured the interference pattern of the first ejected electron using the COLTRIMS reaction microscope, a principle that Dörner helped develop and makes ultrafast reaction processes visible to atoms and molecules. Along with the disruption pattern, COLTRIMS reaction microscopes also allowed the determination of the hydrogen molecule orientation. Researchers here have taken advantage of the fact that the second electron also leaves a hydrogen molecule, so that the remaining hydrogen nuclei can fly and be seen.
“Because we know the spatial orientation of the hydrogen molecule, we used the interference of two electron waves to accurately calculate when the photon reached the first and when the second hydrogen atom was reached,” Sven Grundmann explained that the doctor’s dissertation was forms the scientific article on Science. “And this is up to 247 zeptoseconds, depending on how far apart the molecule the two atoms are from light perception.”
Professor Reinhard Dörner adds: “We observed for the first time that the electron shell in a molecule does not respond to light anywhere at the same time. Time delays occur because information inside the molecule only spreads at the speed of light. In this search, we expanded our COLTRIMS technology to another application. “
References: “Zeptosecond birth time delay in putting molecular lula” by Sven Grundmann, Daniel Trabert, Kilian Fehre, Nico Strenger, Andreas Pier, Leon Kaiser, Max Kircher, Miriam Weller, Sebastian Eckart, Lothar Ph. H. Schmidt, Florian Trinter, Till Jahnke, Markus S. Schöffler and Reinhard Dörner, October 16, 2020, Science.
DOI: 10.1126 / science.abb9318