Back in 1999, the Egyptian chemist Ahmed Zewail was awarded the Nobel Prize for measuring the rate at which molecules change their shape, establishing in the process of femtochemistry. Its measurements were performed in femtoseconds, where one femtosecond is equal to 0.000000000000001 seconds or 10-15 seconds.
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Now, almost two decades later, atomic physicists at Goethe University, led by Professor Reinhard Derner, have for the first time calculated a process that is shorter than femtoseconds: measuring how long a photon takes to cross a hydrogen molecule.
This is the shortest time period ever measured, and is approximately 247 ceptoseconds (trillionth of a billionth of a second or 10-21 seconds). To do this, the scientists irradiated the hydrogen molecule with X-rays from an X-ray laser source PETRA III on a Hamburg accelerator DESY. They set it up so that one photon was enough to eject both electrons from the hydrogen molecule.
The scientists then calculated the interference pattern of the first ejected electron using a COLTRIMS reaction microscope. This device was partially developed by Derner, and it makes visible ultra-fast reaction processes in atoms and molecules.
“Because we knew the spatial orientation of the hydrogen molecule, we used the interference of two electron waves to accurately calculate when a photon reached the first and when it reached the second hydrogen atom,” explains Sven Grundmann, whose doctoral dissertation is based on a scientific paper published in Science.
“And that’s up to 247 ceptoseconds, depending on how far in the molecule the two atoms were in terms of light.”
“We first observed that the electron shell in a molecule does not respond to light everywhere at the same time. The delay time occurs because the information inside the molecule propagates only at the speed of light. With this finding, we have expanded our COLTRIMS technology for another application,” said Professor Reinhard Derner.