Zeptoseconds: new world record in short time measurement

October 16, 2020

FRANKFURT. In 1999, the Egyptian chemist Ahmed Zewail received the Nobel Prize for measuring the speed at which molecules change their shape. He founded femtochemistry using ultrashort laser flashes: the formation and breakup of chemical bonds occurs in the realm of femtoseconds. A femtosecond equals 0.000000000000001 seconds, or 10 exp -15 seconds.

Now atomic physicists at Goethe University in Professor Reinhard Dörner's team have for the first time studied a process that is shorter than femtoseconds by magnitudes. They measured how long it takes for a photon to cross a hydrogen molecule: about 247 zeptoseconds for the average bond length of the molecule. This is the shortest timespan that has been successfully measured to date.

The scientists carried out the time measurement on a hydrogen molecule (H2) which they irradiated with X-rays from the X-ray laser source PETRA III at the Hamburg accelerator facility DESY. The researchers set the energy of the X-rays so that one photon was sufficient to eject both electrons out of the hydrogen molecule.

Electrons behave like particles and waves simultaneously, and therefore the ejection of the first electron resulted in electron waves launched first in the one, and then in the second hydrogen molecule atom in quick succession, with the waves merging.

The photon behaved here much like a flat pebble that is skimmed twice across the water: when a wave trough meets a wave crest, the waves of the first and second water contact cancel each other, resulting in what is called an interference pattern.

The scientists measured the interference pattern of the first ejected electron using the COLTRIMS reaction microscope, an apparatus that Dörner helped develop and which makes ultrafast reaction processes in atoms and molecules visible. Simultaneously with the interference pattern, the COLTRIMS reactions microscope also allowed the determination of the orientation of the hydrogen molecule. The researchers here took advantage of the fact that the second electron also left the hydrogen molecule, so that the remaining hydrogen nuclei flew apart and were detected.

"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," explains Sven Grundmann whose doctoral dissertation forms the basis of the scientific article in Science. "And this is up to 247 zeptoseconds, depending on how far apart in the molecule the two atoms were from the perspective of light."

Professor Reinhard Dörner adds: "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."
-end-


Goethe University Frankfurt

Related Electron Articles from Brightsurf:

Attosecond boost for electron microscopy
A team of physicists from the University of Konstanz and Ludwig-Maximilians-Universit√§t M√ľnchen in Germany have achieved attosecond time resolution in a transmission electron microscope by combining it with a continuous-wave laser -- new insights into light-matter interactions.

Understanding electron transport in graphene nanoribbons
New research published in EPJ Plus aims to better understand the electron transport properties of graphene nanoribbons (GNRs) and how they are affected by bonding with aromatics - a key step in designing technology such as chemosensors.

Efficient valves for electron spins
Researchers at the University of Basel in collaboration with colleagues from Pisa have developed a new concept that uses the electron spin to switch an electrical current.

Measuring electron emission from irradiated biomolecules
Through a study published in EPJ D, researchers have successfully determined the characteristics of electron emission when high-velocity ions collide with adenine - one of the four key nucleobases of DNA.

Exploring mass dependence in electron-hole clusters
A study published in EPJ B reveals that the behaviour of one type of three-particle cluster displays a distinct relationship with the ratio between the masses of its particles.

Attosecond control of an atomic electron cloud
Researchers at SAGA Light Source, the University of Toyama, Hiroshima University and the Institute for Molecular Science have demonstrated a method to control the shape and orientation of an electron cloud in an atom by tuning the attosecond spacing in a double pulse of synchrotron radiation.

Electron correlations in carbon nanostructures
Graphene nanoribbons are only a few carbon atoms wide and have different electrical properties depending on their shape and width.

The fast dance of electron spins
Metal complexes show a fascinating behavior in their interactions with light, which for example is utilized in organic light emitting diodes, solar cells, quantum computers, or even in cancer therapy.

Novel mechanism of electron scattering in graphene-like 2D materials
Suggesting an unconventional way to manipulate the properties of 2D materials in the presence of a Bose-Einstein condensate, and an alternative strategy to design high-temperature superconductors.

Switching electron properties on and off individually
Electrons have different properties - and they all can be used to create order in solid objects.

Read More: Electron News and Electron Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.