An intense light pulse interacting with a weakly bound van der Waals cluster consisting of thousands of atoms can eventually lead to the explosion of the cluster and its complete disintegration. During this process, novel ionization mechanisms occur that are not observed in atoms. With a light pulse that is intense enough, many electrons are removed from their atoms that can move within the cluster, where they form a plasma with the ions on the nanometer scale, a so called nanoplasma. Due to collisions between the electrons, some of them may eventually gain sufficient energy to leave the cluster. A large part of the electrons, however, will remain confined to the cluster. It was theoretically predicted that electrons and ions in the nanoplasma recombine to form Rydberg atoms, however, an experimental proof of this hypothesis is still missing. Previous experiments were carried out at large scale facilities like free-electron lasers that have sizes from a few hundred meters to a few kilometers showing already surprising results such as the formation of very high charge states when an intense XUV pulse interacts with the cluster. However, the accessibility to such sources is strongly limited, and the experimental conditions are extremely challenging. The availability of intense light pulses in the extreme-ultraviolet range from an alternative source is therefore important to gain a better understanding of the various processes occurring in clusters and other extended systems such as biomolecules exposed to intense XUV pulses.
Scientists from the Max-Born-Institut have developed a new light source that is based on the process of high-order harmonic generation. In the experiment, an intense pulse in the extreme-ultraviolet range with a duration of 15 fs (1fs=10-15s) interacted with clusters consisting of argon or xenon atoms. In the current issue of Physical Review Letters (Vol. 112-073003 publ. 20 February 2014) http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.073003 Bernd Schütte, Marc Vrakking and Arnaud Rouzée present the results of these studies, which are in very good agreement with previously obtained results from free-electron lasers: the formation of a nanoplasma was inferred by measuring the kinetic energy distributions of electrons formed in the cluster ionization process, showing a characteristic plateau up to a maximum kinetic energy given by the kinetic energy resulting from photoionization of an individual atom. In collaboration with the theoreticians Mathias Arbeiter and Thomas Fennel from the University of Rostock, it was possible to numerically simulate the ionization processes in the cluster and to reproduce the experimental results. In addition, by using the velocity map imaging technique, a yet undiscovered distribution of very slow electrons was observed and attributed the formation of high-lying Rydberg atoms by electron-ion recombination processes during the cluster expansion. Since the binding energies of the electrons are very small, the DC detector electric field used in the experiment was strong enough to ionize these Rydberg atoms, leading to the emission of low energy electrons. This process is also known as frustrated recombination and could now be confirmed experimentally for the first time. The current findings may also explain why in recent experiments using intense X-ray pulses, high charge states up to Xe26+ were observed in clusters, although a large number of recombination processes is expected to take place. Moreover, the opportunity to carry out this type of experiment with a high-order harmonic source makes it possible in the future to perform pump-probe experiments in clusters and other extended systems with a time resolution down to the attosecond range.
Bernd Schütte, Mathias Arbeiter, Thomas Fennel, Marc J. J. Vrakking and Arnaud Rouzée, "Rare-gas clusters in intense extreme-ultraviolet pulses from a high-order harmonic source", Physical Review Letters 112, (2014)
Dr. Bernd Schütte, +49 (0)30 6392 1248
Prof. Marc J. J. Vrakking, +49 (0)30 6392 1200
Dr. Arnaud Rouzée, +49 (0)30 6392 1240
Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI)
Karl-Heinz Karisch | Forschungsverbund Berlin e.V.
Introducing the disposable laser
04.05.2016 | American Institute of Physics
New fabrication and thermo-optical tuning of whispering gallery microlasers
04.05.2016 | Okinawa Institute of Science and Technology (OIST) Graduate University
Using an ultra fast-scanning atomic force microscope, a team of researchers from the University of Basel has filmed “living” nuclear pore complexes at work for the first time. Nuclear pores are molecular machines that control the traffic entering or exiting the cell nucleus. In their article published in Nature Nanotechnology, the researchers explain how the passage of unwanted molecules is prevented by rapidly moving molecular “tentacles” inside the pore.
Using high-speed AFM, Roderick Lim, Argovia Professor at the Biozentrum and the Swiss Nanoscience Institute of the University of Basel, has not only directly...
If a person pushes a broken-down car alone, there is a certain effect. If another person helps, the result is the sum of their efforts. If two micro-particles are pushing another microparticle, however, the resulting effect may not necessarily be the sum their efforts. A recent study published in Nature Communications, measured this odd effect that scientists call “many body.”
In the microscopic world, where the modern miniaturized machines at the new frontiers of technology operate, as long as we are in the presence of two...
Researchers from the Max Planck Institute Stuttgart have developed self-propelled tiny ‘microbots’ that can remove lead or organic pollution from contaminated water.
Working with colleagues in Barcelona and Singapore, Samuel Sánchez’s group used graphene oxide to make their microscale motors, which are able to adsorb lead...
Neutron scattering and computational modeling have revealed unique and unexpected behavior of water molecules under extreme confinement that is unmatched by any known gas, liquid or solid states.
In a paper published in Physical Review Letters, researchers at the Department of Energy's Oak Ridge National Laboratory describe a new tunneling state of...
Honeycomb structures as the basic building block for industrial applications presented using holo pyramid
Researchers of the Alfred Wegener Institute (AWI) will introduce their latest developments in the field of bionic lightweight design at Hannover Messe from 25...
27.04.2016 | Event News
15.04.2016 | Event News
12.04.2016 | Event News
04.05.2016 | Physics and Astronomy
04.05.2016 | Physics and Astronomy
04.05.2016 | Materials Sciences