What even Einstein didn't know

Kienberger's team has developed a measurement method that allows to determine the time between the recording of an X-ray photon and the emission of an electron. A. Heddergott/ TUM

When a solid body is irradiated with X-rays, electrons separate from it and move towards the surface. But how long does this take? This question was investigated by the international research team led by Prof. Reinhard Kienberger from the Chair of Laser and X-ray Physics at the TUM, who comes from the province of Salzburg.

This is because in the past, only the direction and energy of the electrons could be determined. Previously, the path of the electrons, e.g. through a crystal, could not be observed due to its microscopic dimensions and the extremely short duration of the process.

Iodine atoms used as stopwatches

However, the international team developed a new measuring method which now allows the time between the absorption of an X-ray photon and the emission of an electron to be determined. For this purpose, the physicists “glued” individual iodine atoms to a tungsten crystal and exposed it to X-ray flashes which triggered the photoelectric effect. Because the iodine atoms react extremely quickly to incident X-rays, they serve as light and electron stopwatches.

In order to increase the precision of the measurement, these stopwatches were then calibrated in a further experiment with an only recently developed absolute reference (see second publication below). “This allows the emission of the photoelectrons from a crystal to be determined with an accuracy of a few attoseconds”, says Reinhard Kienberger. An attosecond is a billionth of a billionth of a second.

The measurement shows that photoelectrons from the tungsten crystal can be generated in around 40 attoseconds — around twice as fast as expected. This is due to the fact that light of certain colors interacted primarily with the atoms in the uppermost level of the tungsten crystal.

Another interesting effect was also observed during the experiment: Electrons from atoms on the surface of a crystal are freed even faster. Upon being irradiated with X-rays, they immediately released electrons without a measurable delay. This could be interesting for the manufacturing of particularly quick photocathodes for an application in a free-electron laser, concluded the TUM researchers, as they now know how to accelerate or manipulate the photon-electron conversion.

Furthermore, the new method can also be used to examine the behavior of complicated molecules on surfaces — a promising approach to e.g. develop innovative new solar cells. With the knowledge of these hitherto unknown photochemical processes, technical applications can now be optimized even further.

Prof. Dr. Reinhard Kienberger
Physik-Department E11
Technical University of Munich
Phone: +49 89 289 12840
Mail: reinhard.kienberger@tum.de

M. Ossiander, J. Riemensberger, S. Neppl, M. Mittermair, M. Schaeffer, A. Duensing, M. S. Wagner, R. Heider, M.Wurzer, M. Gerl, M. Schnitzenbaumer, J.V. Barth, F. Libisch, C. Lemell, J. Burgdoerfer, P. Feulner, R. Kienberger: Absolute Timing of the Photoelectric Effect, Nature 09/2018.

M. Ossiander, F. Siegrist, V. Shirvanyan, R. Pazourek, A. Sommer, T. Latka, A. Guggenmos, S. Nagele, J. Feist, J. Burgdörfer, R. Kienberger and M. Schultze:
Attosecond correlation dynamics, Nature physics, 7. November 2016. DOI: 10.1038/nphys3941

https://www.tum.de/nc/en/about-tum/news/press-releases/detail/article/34949/

Media Contact

Dr. Ulrich Marsch Technische Universität München

All latest news from the category: Physics and Astronomy

This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.

innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors