Physicists Reach New Record With Shortest Time Measurement Yet

Schematic representation of zeptosecond measurement. Sven Grundmann, Goethe University Frankfurt

Researchers at Goethe University have measured the shorted interval of time yet: 247 zeptoseconds. A zeptosecond is equivalent to a trillionth of a billionth of a second and the new measurement is over three times smaller than the previous record established in 2016.

To give you a more tangible idea, the difference between this time and a single second is like a few centimeters or an inch and tens of light-years. Or it is roughly the split-second time it takes a person behind you to press the car horn after a long traffic light.

As reported in Science, the research team used a molecule made of two hydrogens, the simplest and most abundant atom in the universe. They then measured how long it takes for photons to cross the molecule and found it to be 247 zeptoseconds.

The measurement is underpinned by some of the peculiarities of the quantum world. Firstly, that electrons behave both as waves and as particles, just like light. Secondly, it is possible to kick an electron away from its atom by shining a light of a certain energy. In this case, they used powerful X-rays.

Each hydrogen atom has a single electron located in a shell surrounding the atomic nucleus. A hydrogen molecule has nuclei and two electrons. The X-ray photons first kicked one electron out and then the other. Like two waves in a pond, the electrons produced an interference pattern made of crests and valleys. That specific pattern informed the team of how fast the photon moved through the molecule.

“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,” lead author Sven Grundmann said 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 orientation of the hydrogen molecule and the detection of the first escaping electron was possible with the COLTRIMS reactions microscope, a technology that team leader Professor Reinhard Dörner helped develop.

“We observed for the first time that the electron shell in a molecule does not react to light everywhere at the same time,” Dörner explained. “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.”


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