Scientists have measured the smallest amount of time ever, the zeptosecond

A zeptosecond is one trillionth of a billionth of a second

Adam Smith
Tuesday 20 October 2020 10:33 BST

A zeptosecond, the shortest amount of time ever recorded, has just been measured by scientists.

It represent one trillionth of a billionth of a second (10-21 seconds).

Physicists from Goethe University Frankfurt used this measurement to record how long it takes for a photon to cross a hydrogen molecule - approximately 247 zeptoseconds.

In order to measure this event, scientists irradiated a hydrogen molecule using  X-rays from the PETRA III laser, the most powerful light source of its kind.

The energy of the X-rays was set so that only one photon was needed to send both electrons out of the hydrogen molecule.

This had the effect of skimming the photon across the two electrons. Electrons behave like particles and waves simultaneously, and as such when one electron was ejected, the waves moved the second electron.

The waves from the second electron merged with the first, and the photon could move across this interference pattern.

By measuring this pattern using a Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) reaction microscope, and with the knowledge of where the hydrogen molecule was, the scientists could record the time it took the photon to move.

"Since we knew the spatial orientation of the hydrogen molecule, we used the interference of the two electron waves to precisely calculate when the photon reached the first and when it reached the second hydrogen atom," said Ph.D. candidate Sven Grundmann in a statement.

"And this is up to 247 zeptoseconds, depending on how far apart in the molecule the two atoms were from the perspective of light."

The speed of these reactions is staggering compared to other molecular actions. In the 1990s, Egyptian chemist Ahmed Zewail measured the speed of which molecules change shape.

Comparatively, these actions are much slower, taking femtoseconds – or 10-15 seconds – to occur.

"We observed for the first time that the electron shell in a molecule does not react to light everywhere at the same time. The time delay occurs because information within the molecule only spreads at the speed of light. With this finding we have extended our COLTRIMS technology to another application," Professor Reinhard Dörner said.

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