11-May-2012 - Max-Planck-Institut für Quantenoptik

Billard game in an atom

Physicists from the Max Planck Institute of Quantum Optics trace the double ionization of argon atoms on attosecond time scales

When an intense laser pulse interacts with an atom it generates agitation on the micro scale. A rather likely outcome of this interaction is single ionization, where one electron is ejected from the atom. From time to time, however, two electrons can be removed from the atom, resulting in the more complex process of double ionization. The detailed course of this process on attosecond time scales (an attosecond is a billionth of a billionth of a second) has been observed by an international team lead by researchers from the Laboratory for Attosecond Physics at the Max Planck Institute of Quantum Optics in close collaboration with colleagues from the Max Planck Institute for Nuclear Physics.

The process is reminiscent of a billiard game, where, after a collision, a ball brings another one in motion. The so called non-sequential double ionization investigated by the researchers bears many similarities with such a billiard ball collision. The strong laser light first ejects an electron from the atom, accelerates it away from and then back towards the atomic core. During the collision the electron transfers part of its energy onto a second electron, which is promoted into an excited state of the core. A little later, the electric field of the laser pulse also liberates the second electron from the atomic core. The non-sequential double ionization usually consists of many such recollision and excitation events, which hampers the interpretation of experimental results.

In close collaboration with colleagues from the Max Planck Institute for Nuclear Physics scientists from the Laboratory for Attosecond Physics at the Max Planck Institute of Quantum Optics and international collaborators have now succeeded in confining such a non-sequential double ionization to a single recollision and excitation event allowing for tracing this process on attosecond time scales.

To achieve this, the scientists sent a four femtosecond long laser pulse onto argon atoms (a femtosecond is a millionth of a billionth of a second). The light wave of this pulse essentially consisted of two wave maxima and two wave minima, i.e two cycles. Due to the action of the laser field, most atoms were singly ionized. Every thousandth atom, however, underwent non-sequential double ionization: After the ionization of the first electron just after the first wave maximum, it took approximately 1.8 femtoseconds for it to revisit the atomic core and excite a second electron. The electron stayed in the excited state for about 400 attoseconds before the laser field released it from the core just before the second wave maximum. „We were surprised to see that the second electron leaves the atomic core 200 attoseconds before the maximum of the second cycle“, said Boris Bergues, a scientist in the LAP-Team. It was assumed so far that the second electron escapes the atomic core at the maximum of a cycle.

Through their observations, the scientists gave a deep insight into the quantum dynamics of a laser-driven multi-electron system. Following such dynamics on attosecond time scales is essential for refining our fundamental understanding of matter-light interactions. Application of the experimental technique to the study of molecules might shed light, one day, on more complex 'billiard games' played by multiple electrons in the course of chemical reaction.

  • Boris Bergues et al.; Attosecond Tracing of Correlated Electron-Emission in Non-Sequential Double Ionization, Nature Communications, 8. Mai 2012
Facts, background information, dossiers
  • Max-Planck-Gesellschaft
More about MPI für Quantenoptik
  • News

    Innovative Blood Test Based on Infrared Light

    A new study carried out by a team of laser physicists, molecular biologists and physicians based at LMU Munich and the Max Planck Institute for Quantum Optics has confirmed the temporal stability of the molecular composition of blood in a population of healthy individuals. The data provide ... more

    The next phase of the proton puzzle

    Scientists at the Max Planck Institute of Quantum Optics (MPQ) have succeeded in testing quantum electrodynamics with unprecedented accuracy to 13 decimal places. The new measurement is almost twice as accurate as all previous hydrogen measurements combined and moves science one step closer ... more

    Laser takes pictures of electrons in crystals

    Microscopes of visible light allow us to see tiny objects such living cells and their interior. Yet, they cannot discern how electrons are distributed among atoms in solids. Now researchers around Prof. Eleftherios Goulielmakis of the Extreme Photonics Labs at the University of Rostock and ... more

More about Max-Planck-Gesellschaft
  • News

    Structure of key protein for cell division puzzles researchers

    Human cell division involves hundreds of proteins at its core. Knowing the 3D structure of these proteins is pivotal to understand how our genetic material is duplicated and passed through generations. The groups of Andrea Musacchio and Stefan Raunser at the Max Planck Institute of Molecula ... more

    A new method for exploring the nano-world

    Scientists at the Max Planck Institute for the Science of Light (MPL) and Max-Planck-Zentrum für Physik und Medizin (MPZPM) in Erlangen present a large step forward in the characterization of nanoparticles. They used a special microscopy method based on interfereometry to outperform existin ... more

    Finding new weapons in Nature`s battlesites

    Interactions between microbes and other organisms are mediated by a plethora of small molecules, also called natural products. A research team led by Dr. Yi-Ming Shi and Prof. Helge Bode from the Max Planck Institute for Terrestrial Microbiology has now performed a systematic analysis of bi ... more

More about MPI für Kernphysik
  • News

    Mass of the deuteron corrected

    High-precision measurements of the mass of the deuteron, the nucleus of heavy hydrogen, provide new insights into the reliability of fundamental quantities in atomic and nuclear physics. This is reported in the journal "Nature" by a collaboration led by the Max Planck Institute for Nuclear ... more

    Weighing an ant on top of an elephant: Quantum jump tipping the balance

    A new door to the quantum world: when an atom absorbs or releases energy via the quantum jump of an electron, it becomes heavier or lighter, according to Einstein’s theory of relativity (E = mc²). However, the effect is minuscule for a single atom. Nevertheless, the team of Klaus Blaum and ... more

    Quantum logic spectroscopy unlocks potential of highly charged ions

    Scientists from the Physikalisch-Technische Bundesanstalt (PTB) and the Max Planck Institute for Nuclear Physics (MPIK) have carried out pioneering optical measurements of highly charged ions with unprecedented precision. To do this, they isolated a single Ar¹³⁺ ion from an extremely hot pl ... more