Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

X-ray laser reveals chemical reaction

15.03.2013
What happens when a chemical bond is broken? That question was recently answered with the help of a so-called free electron x-ray laser, which makes it possible to follow in real time how bindings in a molecule are changed and broken.
The study, published in Science, found, among other things, evidence of a much-discussed intermediate state before molecules bind to or leave a metal surface. The possibility of monitoring at the molecular level how the electron structure changes in a chemical reaction creates entirely new opportunities for investigating and understanding key chemical processes in detail.

“To identify and characterize short-lived intermediate states in chemical reactions on the surface of metals has long been a dream,” says Henrik Öström at the Department of Physics, Stockholm University, who is part of the international research team that carried out the study. “With the new free electron x-ray laser at SLAC, we have shown that dreams can become reality and managed to identify a short-lived intermediate state when the bindings of CO molecules to a metal surface are broken or created.

SLAC (Stanford Linear Accelerator Center) was long a flagship of particle physics, where electrons were accelerated to nearly the speed of light in a three-kilometer-long linear accelerator. Now the accelerator has been rebuilt to generate, instead, powerful ultra-short (10-100 femtosecond) pulses of x-ray beams with a wavelength that makes it possible to examine the surroundings of a molecule down to the level of an individual atom. The pulses are sufficiently short to provide a snapshot of the electron distribution around the atom. By varying the delay between the start of a reaction and when the distribution of electrons is monitored with the x-ray pulse, these scientists can create a suspended-time image of changes in the course of the reaction.

“A first challenge was whether the incredibly powerful pulse would destroy the sample,” explains Anders Nilsson, a professor of synchrotron-light physics at SLAC and an adjunct professor at Stockholm University. “However, it turned out to be entirely possible to adjust the experiment in a way that enabled us to make our measurements.”

Caption: The x-ray laser investigates the change in the electron structure when CO molecules desorb from a metal surface of ruthenium. Roughly 30% of the molecules are pumped up with the aid of a femtosecond of optic laser from the surface-bonded (“chemisorbed”) state to a transient intermediate state (“precursor”) where they interact faintly with the surface. By examining the molecules with the x-ray laser with varying delay periods, it is possible to show that the time scale for achieving the precursor state is a few picoseconds and that they exist there for a few tens of picoseconds before either leaving the surface entirely or returning to the surface.

In the experiment, CO molecules were dosed onto a metal surface of ruthenium, which is used in automobile catalytic converters, for instance. CO binds strongly to the surface but can be made to let go by heating up the surface, which was done with a pulse from an optical laser. By starting the reaction for all the molecules at the same time, the team got a sufficient number of molecules to simultaneously enter a state where they have almost let go of the surface but still have a weak binding to it. From this short-lived state, the molecules can then continue out into a gas phase or renew their bond when the surface cools down again.

“Scientists have long speculated whether such a state, a so-called ‘precursor,’ exists. The new experiment is the first to directly show its existence,” says Lars G. M. Pettersson at the Department of Physic, Stockholm University. These studies will not go on to more complex reactions of interest to the field of synthetic fuels, among other applications.

Besides the researchers from Stockholm University, scientists from Stanford University, SLAC, the University of Hamburg, the Technical University of Denmark, the Helmholtz Center in Berlin, and the Fritz Haber Institute in Berlin.

Article; Science 15 March 2013: 1302-1305. [DOI:10.1126/science.1231711]
Further information:
Henrik Öström at the Department of Physics, Stockholm University, phone: +46 (0)8 5537 8641 mobile: +46 (0)73 035 9150 e-mail: ostrom@fysik.su.se

Lars G.M. Pettersson at the Department of Physics, Stockholm University, phone: +46 (0)8 5537 8712 mobile: +46 (0)70 495 1990 e-mail: lgm@fysik.su.se

Anders Nilsson at SLAC and Stockholm University, phone: +1 650 926 2233 e-mail: nilsson@slac.stanford.edu

Pressofficer Viktor Sandqvist, e-mail: viktor.sandqvist@su.se, phone +46-767 852 172

Viktor Sandqvist | idw
Further information:
http://www.su.se
http://www.vr.se

More articles from Physics and Astronomy:

nachricht DGIST develops 20 times faster biosensor
24.04.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)

nachricht New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of 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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

DGIST develops 20 times faster biosensor

24.04.2017 | Physics and Astronomy

Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging

24.04.2017 | Materials Sciences

Atomic-level motion may drive bacteria's ability to evade immune system defenses

24.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>