Placed in fire detectors and water treatment units UV-sensors can save lives; also in many areas of industry and environment the demand for these devices is rising steadily. Scientists of Kiel University have been able to ”bake” nanostructures within seconds, in order to fabricate very fast ... more
Watching the quantum race of electrons
For the first time ever, a German team of physicists has observed the race of two electrons that are liberated from atoms in the course of photoionization, i.e. under the influence of laser radiation. In order to resolve the electron’s movement during only 50 femtoseconds, scientists from Hamburg and Kiel Universities and DESY (Deutsches Elektronen-Synchrotron – one of the world's leading accelerator centres) used an ultra fast terahertz streak camera in combination with a free-electron-laser. The experimental findings will improve the rapidly evolving free-electron-laser technology used in many fields of science – from physics to biology.
The interaction of electrons is crucial for the properties of atoms and molecules which are the building blocks of living organisms and all man-made systems. Understanding the electronic processes in atoms is therefore essential for numerous future applications – from medicine to engineering.
When a photon of sufficiently high energy hits an atom it may kick out an electron. Albert Einstein termed this process “photo ionization” (photo effect) back in 1905 and thus confirmed a theory of the Kiel scientist Max Planck that would soon revolutionize physics: quantum mechanics. Quantum mechanics predicts that the liberated electron runs away from the atom, behaving like a wave. In the 1920s, Lise Meitner and Pierre Auger independently discovered another effect: When applying specific photon energy during photo ionization, a second electron, termed Auger electron, may be liberated from the atom. In cases when the Auger electron runs in the same direction as the first electron a quantum race of electron waves starts.
This race of the two electrons is extremely fast, taking between 1 and 100 femtoseconds (1fs=0.000 000 000 000 001s). “Until now, no experiment has resolved this race in time”, says Professor Markus Drescher of the Institute for Experimental Physics at Hamburg University, leader of the experimental part of the project. The key to observing the electron race in the current study was to combine the free-electron laser FLASH at DESY in Hamburg with an ultrafast streak camera. By accurately controlling the timing of the two electromagnetic fields generated by the laser and the camera, the scientists were able to reconstruct the electrons’ movement and energy exchange. In this manner, the physicists detected how the Auger electron passes the first one.
At the Institute of Theoretical Physics and Astrophysics of Kiel University, the research group of Professor Michael Bonitz tried to reproduce the experimental results with computer simulations. “After testing several possible explanations for the measured results, our PhD student Sebastian Bauch verified that the experiment indeed observed the quantum race of two electrons”, adds Bonitz. The Kiel physicists collaborate with the experimentalists from Hamburg within the project “FLASH” funded by the German Federal Ministry of Education and Research.
The results give valuable information on key properties of the involved laser pulse. The free electron laser technology has been rapidly evolving in recent years. In this context the present results will be important for improving the quality and precision of future free electron laser experiments.
Schütte, B., Bauch, S., Frühling, U., Wieland, M., Gensch, M., Plönjes, E., Gaumnitz, T., Azima, A., Bonitz, M. and Drescher, M.: Evidence for chirped Auger electron emission”, Physical Review Letters
Physicists at Hamburg and Kiel University and the Forschungszentrum Jülich have found for the first time a regular lattice of magnetic skyrmions – cycloidal vortex spin structures of exceptional stability – on a surface. This fascinating magnetic structure was discovered experimentally at t ... more
What happens when a chemical bond is broken? That question was recently answered with the help of a so-called free electron x-ray laser, which makes it possible to follow in real time how bindings in a molecule are changed and broken. The study, published in Science, found, among other thin ... more
For the first time, air-polluting soot particles have been imaged in flight down to nanometre resolution. Pioneering a new technique, the international team, including researchers from DESY, snapped the most detailed images yet of airborne aerosols. “For the first time we can actually see t ... more
Photoinduced chemical reactions are responsible for many fundamental processes and technologies, from energy conversion in nature to micro fabrication by photo-lithography. One process that is known from everyday's life and can be observed by the naked eye, is the exposure of photographic f ... more
A team led by DESY scientists has designed, fabricated and successfully tested a novel X-ray lens that produces sharper and brighter images of the nano world. The lens employs an innovative concept to redirect X-rays over a wide range of angles, making a high convergence power. The larger t ... more
An X-ray study carried out at DESY allows to improve the quality of chocolate. The study offers new insights into the formation of fat bloom, an unwelcome white layer that occasionally forms on chocolate. "Although fat blooming is perfectly harmless, it causes millions in damage to the food ... more
- 1How Natural Channel Proteins Move in Artificial Membranes
- 2Merck’s Acquisition of Sigma-Aldrich Receives Clearance from EU Regulators
- 3Schleicher & Schuell has been purchased by Whatman plc
- 4New composite material as CO2 sensor
- 5Danaher To Acquire Pall Corporation
- 6'Green chemistry' to quantify the components of cosmetics
- 7Thousands of Droplets for Diagnostics
- 8Waters Corporation Announces Christopher J. O'Connell as Chief Executive Officer
- 9Pall Corporation Acquires BioSMB Technology from Tarpon Biosystems
- 10Eurofins signs an exclusive agreement to acquire the Biomnis Group