Featured Research

from universities, journals, and other organizations

Revealing secrets of exploding clusters

Date:
February 24, 2014
Source:
Forschungsverbund Berlin e.V. (FVB)
Summary:
The investigation of cluster explosion dynamics under intense extreme-ultraviolet (XUV) pulses has so far been limited to large scale facilities like free-electron lasers. In a recent publication, it was shown that the research on clusters is now also possible with intense XUV pulses obtained in a laboratory-scale environment with a newly developed light source that makes use of the high-order harmonic generation process. For the first time, the formation of high-lying Rydberg atoms by electron-ion recombination during the cluster expansion initially triggered by an intense XUV pulse was identified, giving new insight into the cluster dissociation process. 

Left side: 2D electron momentum map of argon clusters with an average size of 3500 atoms showing a pronounced central distribution attributed to the ionization of Rydberg atoms with the detector field. Right side: The electron kinetic energy spectrum (black curve) shows a good agreement with numerical calculations, which are displayed for intensities of 5x1011 W/cm2 (red), 1x1012 W/cm2 (green) and 2x1012 W/cm2 (violet).
Credit: MBI

The investigation of cluster explosion dynamics under intense extreme-ultraviolet (XUV) pulses has so far been limited to large scale facilities like free-electron lasers. In a recent publication it was shown that the research on clusters is now also possible with intense XUV pulses obtained in a laboratory-scale environment with a newly developed light source that makes use of the high-order harmonic generation process. For the first time, the formation of high-lying Rydberg atoms by electron-ion recombination during the cluster expansion initially triggered by an intense XUV pulse was identified, giving new insight into the cluster dissociation process.

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, 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.


Story Source:

The above story is based on materials provided by Forschungsverbund Berlin e.V. (FVB). Note: Materials may be edited for content and length.


Journal Reference:

  1. B. Schütte, M. Arbeiter, Th. Fennel, M. J. J. Vrakking, A. Rouzée. Rare-Gas Clusters in Intense Extreme-Ultraviolet Pulses from a High-Order Harmonic Source. Physical Review Letters, 2014; 112 (7) DOI: 10.1103/PhysRevLett.112.073003

Cite This Page:

Forschungsverbund Berlin e.V. (FVB). "Revealing secrets of exploding clusters." ScienceDaily. ScienceDaily, 24 February 2014. <www.sciencedaily.com/releases/2014/02/140224105907.htm>.
Forschungsverbund Berlin e.V. (FVB). (2014, February 24). Revealing secrets of exploding clusters. ScienceDaily. Retrieved April 18, 2014 from www.sciencedaily.com/releases/2014/02/140224105907.htm
Forschungsverbund Berlin e.V. (FVB). "Revealing secrets of exploding clusters." ScienceDaily. www.sciencedaily.com/releases/2014/02/140224105907.htm (accessed April 18, 2014).

Share This



More Matter & Energy News

Friday, April 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) — After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) — An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) — It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com
German Researchers Crack Samsung's Fingerprint Scanner

German Researchers Crack Samsung's Fingerprint Scanner

Newsy (Apr. 16, 2014) — German researchers have used a fake fingerprint made from glue to bypass the fingerprint security system on Samsung's new Galaxy S5 smartphone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins