Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unique insight into molecules

16.06.2014

Processes on the atomic scale can only be described accurately by using the laws of quantum mechanics. Physicists at the University of Würzburg have now succeeded for the first time to completely determine the state of such a quantum mechanical system in experiments.

"It is a major step towards fully understanding the natural processes at the atomic scale." That is the conclusion a group of Würzburg experimental physicists draws in an article recently published in the renowned Nature Communications journal. Achim Schöll, associate professor at the Department of Experimental Physics VII at the University of Würzburg, and his team together with researchers from Jülich and Trieste have found a way to determine the spatial probability density of electrons in a molecule by experiment.
The laws of quantum mechanics


An image representing a cut through a molecule orbital in the real space was impossible to obtain by experiment in the past. Physicists of the University of Würzburg have now made it possible.

Graphic Schöll work Group

"One has to use the laws of quantum mechanics to describe the processes inside atoms or molecules," Achim Schöll explains. Standard school knowledge of electrons orbiting the atomic nucleus on precise orbits - like moon's orbit around Earth - is not very illuminating when it comes to understanding the world of quantum mechanics. There, particles are treated as complex wave functions; their properties are described by the waves' amplitude and phase.

However, it is extremely difficult to measure these two values by experiment: "It is in the nature of measuring that the phase information gets lost in the process," Schöll says. This is because most experiments measure intensities that correspond to the square of the wave function and thus to the spatial probability density. As a result, the phase information, that is the sign of this function, is lost.

Previous experiments have weak points

This is unsatisfactory from the experimental physicists' point of view. After all, the phase is the decisive value in such fundamental processes as chemical bonding or superconductivity. Therefore, there has been intensive research to find a way to measure this value by experiment. A few methods for measuring the phase do exist already. "But they are not capable of determining the spatial distribution of the electrons at the same time," Schöll explains.

The Würzburg experiment

Schöll and his colleagues have now shown in an experiment that it is indeed possible to measure both phase and spatial probability density at the same time. They accomplished their goal using angle-resolved photoelectron spectroscopy with circular polarized light.

In photoelectron spectroscopy, physicists "bombard" the sample with UV light or X-rays to detach electrons from the sample's surface. The direction of emission and the kinetic energy of these electrons allow scientists to draw conclusions, for example, to the chemical composition and the electronic properties of the solid. Depending on the type of examination, they can also fit the beam of light with specific properties. "Circular polarized light" in this context means: The plane in which the light wave oscillates turns around on a circle – either clockwise or counter-clockwise.

Symmetry provides the wanted information

"Depending on whether we are irradiating our molecule with right or left polarized light, we obtain different intensity distributions," Schöll explains. The difference of these two intensities, the so-called circular dichroism, then shows characteristic symmetries when changing the light's direction of incidence. This allows the phase of the underlying wave function to be derived. This experiment, too, does not return the phase directly. "But we can determine the symmetry of the phase and thus say where the value is positive and where negative," the physicist continues.

Combined with the measurement results of the spatial probability density, the physicists thus get a picture corresponding to a cut through a molecule orbital in the real space. And to know the molecule orbital means to know the molecule's properties as well.

Complete determination of molecular orbitals by measurement of phase symmetry and electron density. M. Wiener, D. Hauschild, C. Sauer, V. Feyer, A. Schöll & F. Reinert. Nature Communications, Published 9 June 2014; DOI: 10.1038/ncomms5156

Contact

Dr. Achim Schöll, T: (0931) 31-85127; achim.schoell@physik.uni-wuerzburg.de

Gunnar Bartsch | idw - Informationsdienst Wissenschaft
Further information:
http://www.uni-wuerzburg.de

Further reports about: Communications electrons experiments function measurement spatial spectroscopy

More articles from Physics and Astronomy:

nachricht Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

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: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>