Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Group dynamics of atoms -- DESY scientists observe the collective Lamb shift for the first time

14.05.2010
An ensemble of identical atoms submitted to irradiation of light behaves differently than a single atom. Jointly, the atoms emit light at a lower frequency than a single atom would do.

This effect, the so-called collective Lamb shift, was recently observed by a research team headed by Dr. Ralf Röhlsberger from the Helmholtz research centre DESY. The scientists from DESY, ESRF (France) and University of Leuven (Belgium) provided evidence of an effect that theorists predicted already more than 35 years ago, but could not be experimentally proved so far. The results of this experiment carried out at ESRF in Grenoble are published in the current issue of Science.

The Lamb shift is a small difference of the oscillation frequency of electrons in the atom. It becomes visible when light excites atoms to radiate. The frequency shift occurs when the excited atom emits and re-absorbs its light several times before returning to its ground state. The discovery of the Lamb shift in hydrogen in 1947 laid the foundation for the development of quantum electrodynamics (QED) as a unified theory of interaction of light and matter. For this discovery, the physicist Willis Lamb received the Nobel Prize in 1955.

When an ensemble of identical atoms is excited to radiate, it is possible that the emitted light of an atom is not only absorbed and re-emitted by the single atom but also by other atoms of the ensemble. Therefore, the light emitted by these atoms has a lower energy and exhibits a distinct red shift compared to the light that a single isolated atom would emit.

For their experiments, Röhlsberger and his team of researchers developed a new measurement method. They placed an ensemble of 57Fe atoms between two platinum mirrors separated only by a few nanometres and irradiated this array with X-ray radiation. And in fact, the predicted collective frequency shift could be measured in this way, even though it was believed for a long time that the atoms must not be separated by more than a wavelength. The researchers’ group took advantage of the fact that that the radiation of 57Fe atoms is enormously intensified, making the collective Lamb shift clearly visible. With the help of Mössbauer spectroscopy, the shift could be determined very precisely. The measured values are in excellent agreement with theoretical predictions.

This experimental method also offers new possibilities to study collective effects in the interaction of light and matter. Thus, the researchers observed that the light from the ensemble of atoms was emitted almost 100 times faster than from a single isolated atom. This phenomenon is called superradiance. Superradiance enables a very efficient energy transfer between light and matter and it may play an important role for designing more efficient solar cells and in fast optical information processing.

Dr. Thomas Zoufal | idw
Further information:
http://www.desy.de/

More articles from Physics and Astronomy:

nachricht New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology

nachricht Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>