14-Aug-2015 - Ludwig-Maximilians-Universität München (LMU)

Attosecond Electron Catapult

A team of physicists and chemists from the University of Rostock, the Laboratory of Attosecond Physics at the Ludwig-Maximilians-Universität, the Max Planck Institute of Quantum Optics, and Freie Universität Berlin has studied the interaction of light with tiny glass particles.

The relationship between strong laser pulses and glass nanoparticles is a special one – one that could influence medical methods, as scientists from Rostock, Munich, and Berlin have discovered. The interplay between light and matter was studied by a team of physicists and chemists from the Laboratory of Attosecond Physics (LAP) at the Max Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität Munich (LMU), from the Institute of Physics of the University of Rostock, and from Freie Universität Berlin. The researchers studied the interaction between strong laser pulses and glass nanoparticles, which consist of multiple millions of atoms. Depending on how many atoms were contained in the nanoparticles, these objects reacted differently over attosecond timescales. Depending on their size, so called near-fields (electromagnetic fields close to the particle surface) were induced by the laser pulses, resulting in a controlled directional emission of electrons. These findings could eventually extend cancer therapy and imaging methods in medicine.
Strong laser pulses have an extremely pronounced effect on nanoparticles. As soon as the atoms “feel” the electromagnetic wave of the light, their electrons start to oscillate. This produces near-fields at the surface of the particles. These near-fields have dimensions in the nanometer range, and oscillate in a characteristic fashion depending on the wavelength of the incident light.

Led by Prof. Matthias Kling, the LAP-physicists studied silica nanospheres with diameters of 50 to 550 nanometers, which were chemically synthesized in the research group around Eckart Rühl at Freie Universität Berlin. The scientists let strong, approximately four-femtosecond-long laser pulses hit the group of atoms. As soon as the electromagnetic waves of the light field hit the nanospheres, near-fields formed at the surface and began to pulsate. The larger the light-irradiated spheres were compared to the laser wavelength (720 nanometers), the stronger the effect of the near-fields as an electron catapult.

The researchers observed this effect by using particle detectors to monitor the flight paths of electrons emitted from the near-fields of the nanospheres within the passage of the laser pulse. “The energy and direction of emitted electrons is strongly linked to the spatial and temporal structure of the near-fields. The emission of electrons is like a ping-pong game on the surface of the nanospheres that can be controlled with a precision of attoseconds,” explains Prof. Thomas Fennel from the University of Rostock. He conducted simulations with his team, shedding light on the microscopic processes and their evolution in time. “First, the electrons leave the spheres, but they are then pulled back to their surface. After bouncing off the surface, they obtain a strong, final momentum kick from the near-field, which frees them from the nanoparticles,” Prof. Matthias Kling added.

Since the directional emission of particles can be controlled with this technique using laser light, the researchers argue that a long-term perspective could be medical applications. “With directional electron motion, strongly directed X-rays for imaging applications could be produced,” describes Prof. Eckart Rühl. With sufficiently intense laser pulses, it may also be possible to release ions, which are charged atoms, from the nanocomposite, resulting in strongly directed ion radiation for cancer therapy. Furthermore, the technique might open up new perspectives for material processing beyond the diffraction limit – for instance in order to remove nanometer-sized areas from a surface.

Facts, background information, dossiers
  • attosecond physics
  • Freie Universität Berlin
  • Universität Rostock
  • MPI für Quantenoptik
  • LMU
More about LMU
  • News

    Most powerful dual-comb spectrometer developed

    Scientists from Hamburg and Munich developed the world's most powerful dual-comb spectrometer that paves the way for many applications in atmospheric science and biomedical diagnostics, such as early cancer detection. The work has recently been published in Nature Communications. The core p ... more

    Light-Controlled Reactions at the Nanoscale

    Controlling strong electromagnetic fields on nanoparticles is the key to triggering targeted molecular reactions on their surfaces. Such control over strong fields is achieved via laser light. Although laser-induced formation and breaking of molecular bonds on nanoparticle surfaces have bee ... more

    Early Earth: Evolution in the abiotic world

    Chemical evolution took place on the early Earth before the biological one: Out of simple abiotic molecules, there emerged increasingly complex networks of chemical reactions and ultimately the first building blocks of life. Analogously to its biological counterpart, chemical evolution is b ... more

More about Uni Rostock
More about Freie Universität Berlin
  • News

    Physicists develop miniature terahertz sources

    Researchers at Martin Luther University Halle-Wittenberg (MLU) and Freie Universität Berlin have developed a new, simple approach for generating terahertz radiation. Strong optical laser pulses enable terahertz electromagnetic fields to be generated directly at a specific point. The team ha ... more

    Good Quantum States and Bad Quantum States

    A theoretical trick allows scientists to describe quantum states of thousands of atoms. If standard methods were used, all storage capacity in the world would not be enough to do this. For a long time, quantum experiments were only carried out with a small number of particles. Even the beha ... more

    An assembly line for medications

    Researchers at the Max Planck Institute of Colloids and Interfaces (MPICI) and the Freie Universität Berlin have succeeded in developing better methods of producing APIs (active pharmaceutical ingredients). As a result, Efavirenz, one of the preferred agents for treating HIV in combination ... more

More about Max-Planck-Gesellschaft
  • News

    More Sustainability with Mechanochemistry

    Flour, coffee or spices: Many people know the principle of a mill from the kitchen. But special mills are also used for research purposes in the laboratories of the Max-Planck-Institut für Kohlenforschung. The scientists are convinced that mechanochemistry can make the chemical industry mor ... more

    Terahertz light from superconducting stripes

    Why do some materials carry electrical currents without any resistance only when cooled to near absolute zero while others do so at comparatively high temperatures? This key question continues to vex scientists studying the phenomenon of superconductivity. Now a team of researchers from And ... more

    Mirror image molecules reveal drought stress in forests

    Worldwide, plants emit about 100 million tonnes of monoterpenes into the atmosphere each year. These volatile organic molecules include many fragrances such as the molecule pinene – known for its pine fresh scent. Since these molecules are highly reactive and can form tiny aerosol particles ... more