Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Laser pulses control single electrons in complex molecules

02.09.2009
Predatory fish are well aware of the problem: In a swarm of small fish it is hard to isolate prey. A similar situation can be found in the microcosm of atoms and molecules, whose behavior is influenced by “swarms” of electrons.

In order to achieve control over single electrons in a bunch, ultrashort light pulses of a few femtoseconds duration are needed. Physicists of the Max Planck Institute of Quantum Optics (MPQ) in Garching and chemists of the Ludwig-Maximilians-Universität (LMU) in Munich succeeded for the first time to use light for controlling single, negatively charged elementary particles in a bunch of electrons.

The scientists achieved a major milestone that they aimed for within the excellence cluster “Munich Center for Advanced Photonics” (MAP). (Physical Review Letters, 1 September 2009).

Electrons are extremely fast moving particles. In atoms and molecules they move on attosecond timescales. An attosecond is only a billionth of a billionth of a second. With light pulses that last only a few femtoseconds down to attoseconds it is possible to achieve control over these particles and to interact with them on the timescale of their motion.

These short light pulses exhibit strong electric and magnetic fields influencing the charged particles. A femtosecond lasts 1000 times longer than an attosecond. In molecules with only a single electron, such as the deuterium molecular ion, their control with such light pulses is relatively easy. This was demonstrated in 2006 by a team of physicists including Professor Marc Vrakking and Dr. Matthias Kling from AMOLF in Amsterdam and Professor Ferenc Krausz in Garching (MPQ).

Scientists led by the junior research group leader Dr. Matthias Kling (MPQ) in collaboration with Professor Marc Vrakking (AMOLF) and Professor Regina de Vivie-Riedle (LMU) have managed to control and monitor the outer electrons from the valence shell of the complex molecule carbon monoxide (CO) utilizing the electric field waveform of laser pulses. Carbon monoxide has 14 electrons. With increasing number of electrons in the molecule the control over single electrons becomes difficult as their states lie energetically very close to each other.

In their experiments the scientists used visible (740 nm) laser pulses with 4 femtoseconds duration. The control was experimentally determined via an asymmetric distribution of C+ and of O+ fragments after the breaking of the molecular bond. The measurement of C+ and O+ fragments implies a dynamic charge shift along the molecular axis in one or the other direction, controlled via the laser pulse.

The femtosecond laser pulses initially detached an electron from a CO molecule. Subsequently the electron was driven by the laser field away from and back to the ion, where it transferred its energy in a collision. The whole process took only ca. 1.7 femtoseconds. ”The collision produces an electronic wave packet which induces a directional movement of electrons along the molecular axis,” says Regina de Vivie-Riedle. ”The excitation and subsequent interaction with the remainder of the intense laser pulse leads to a coupling of electron and nuclear motion and gives a contribution to the observed asymmetry,” explains Matthias Kling.

The scientists could also image the structure and form of the outer two electron orbitals of carbon monoxide via the ionization process. The extremely short femtosecond laser pulses allowed the scientists to explore this process in the outermost orbitals. They found the ionization of the molecules to take place with a distinct angular dependence with respect to the laser polarization direction. This observation was found to be in good agreement with theoretical calculations and also gave a contribution to the observed asymmetry. The scientists could show that the strength of this asymmetry strongly depends on the duration of the laser pulses.

With their experiments and calculations, the researchers from Garching and Munich have achieved an important milestone that they aimed for within the excellence cluster “Munich Center for Advanced Photonics” (MAP). The goals were to achieve and observe the control of single electrons within a multi-electron system.

Electrons are present in all important microscopic biological and technical processes. Their extremely fast motion on the attosecond timescale, determines biological and chemical processes and also the speed of microprocessors – technology at the heart of computing. With their experiments the researchers have made a further, important step towards the control of chemical reactions with light. The results are also related to basic research on lightwave electronics aiming at computing speeds on attosecond timescales.

Full bibliographic information
I. Znakovskaya, P. von den Hoff, S. Zherebtsov, A. Wirth, O. Herrwerth, M.J.J. Vrakking, R. de Vivie-Riedle, M.F. Kling:
“Attosecond control of electron dynamics in carbon monoxide”
Physical Review Letters (online version: EID 103/103002, 1 September 2009)

Julia Zahlten | alfa
Further information:
http://tinyurl.com/nopbx8
http://www.uni-muenchen.de

More articles from Physics and Astronomy:

nachricht Matter falling into a black hole at 30 percent of the speed of light
24.09.2018 | Royal Astronomical Society

nachricht Scientists solve the golden puzzle of calaverite
24.09.2018 | Moscow Institute of Physics and Technology

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: Scientists present new observations to understand the phase transition in quantum chromodynamics

The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.

This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.

Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...

Im Focus: Patented nanostructure for solar cells: Rough optics, smooth surface

Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.

"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...

Im Focus: New soft coral species discovered in Panama

A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.

Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...

Im Focus: New devices based on rust could reduce excess heat in computers

Physicists explore long-distance information transmission in antiferromagnetic iron oxide

Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.

Im Focus: Finding Nemo's genes

An international team of researchers has mapped Nemo's genome

An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

"Boston calling": TU Berlin and the Weizenbaum Institute organize a conference in USA

21.09.2018 | Event News

One of the world’s most prominent strategic forums for global health held in Berlin in October 2018

03.09.2018 | Event News

4th Intelligent Materials - European Symposium on Intelligent Materials

27.08.2018 | Event News

 
Latest News

Matter falling into a black hole at 30 percent of the speed of light

24.09.2018 | Physics and Astronomy

NASA balloon mission captures electric blue clouds

24.09.2018 | Earth Sciences

New way to target advanced breast cancers

24.09.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>