Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Unique insight into molecules


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


Dr. Achim Schöll, T: (0931) 31-85127;

Gunnar Bartsch | idw - Informationsdienst Wissenschaft
Further information:

Further reports about: Communications electrons experiments function measurement spatial spectroscopy

More articles from Physics and Astronomy:

nachricht Laser-wielding physicists seize control of atoms' behavior
06.10.2015 | University of Chicago

nachricht Observing the Unobservable: Researchers Measure Electron Orbitals of Molecules in 3D
05.10.2015 | Karl-Franzens-Universität Graz

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: Physicists shrink particle accelerator

Prototype demonstrates feasibility of building terahertz accelerators

An interdisciplinary team of researchers has built the first prototype of a miniature particle accelerator that uses terahertz radiation instead of radio...

Im Focus: Simple detection of magnetic skyrmions

New physical effect: researchers discover a change of electrical resistance in magnetic whirls

At present, tiny magnetic whirls – so called skyrmions – are discussed as promising candidates for bits in future robust and compact data storage devices. At...

Im Focus: High-speed march through a layer of graphene

In cooperation with the Center for Nano-Optics of Georgia State University in Atlanta (USA), scientists of the Laboratory for Attosecond Physics of the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität have made simulations of the processes that happen when a layer of carbon atoms is irradiated with strong laser light.

Electrons hit by strong laser pulses change their location on ultrashort timescales, i.e. within a couple of attoseconds (1 as = 10 to the minus 18 sec). In...

Im Focus: Battery Production: Laser Light instead of Oven-Drying and Vacuum Technology

At the exhibition BATTERY + STORAGE as part of WORLD OF ENERGY SOLUTIONS 2015 in Stuttgart, the Fraunhofer Institutes for Laser Technology ILT and for Ceramic Technologies and Systems IKTS will be showing how laser technology can be used to manufacture batteries both cost- and energy-efficiently.

In the truest sense, it’s all about watts at the Dresden-based Fraunhofer Institute for Ceramic Technologies and Systems IKTS and the Aachen-based Fraunhofer...

Im Focus: New Sinumerik features improve productivity and precision

EMO 2015, Hall 3, Booth E06/F03

  • Drive optimization called automatically by the part program boosts productivity
  • Automatically switching the dynamic values to rapid traverse and interpolation...
All Focus news of the innovation-report >>>



Event News

EHFG 2015: Securing healthcare and sustainably strengthening healthcare systems

01.10.2015 | Event News

Conference in Brussels: Tracking and Tracing the Smallest Marine Life Forms

30.09.2015 | Event News

World Alzheimer`s Day – Professor Willnow: Clearer Insights into the Development of the Disease

17.09.2015 | Event News

Latest News

Graphene teams up with two-dimensional crystals for faster data communications

06.10.2015 | Information Technology

Laser-wielding physicists seize control of atoms' behavior

06.10.2015 | Physics and Astronomy

Flipping molecular attachments amps up activity of CO2 catalyst

06.10.2015 | Life Sciences

More VideoLinks >>>