Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Movement of pyrrole molecules defy 'classical' physics

29.04.2013
New research shows that movement of the ring-like molecule pyrrole over a metal surface runs counter to the centuries-old laws of 'classical' physics that govern our everyday world.

Using uniquely sensitive experimental techniques, scientists have found that laws of quantum physics - believed primarily to influence at only sub-atomic levels – can actually impact on a molecular level.

Researchers at Cambridge's Chemistry Department and Cavendish Laboratory say they have evidence that, in the case of pyrrole, quantum laws affecting the internal motions of the molecule change the "very nature of the energy landscape" – making this 'quantum motion' essential to understanding the distribution of the whole molecule.

The study, a collaboration between scientists from Cambridge and Rutgers universities, appeared in the German chemistry journal Angewandte Chemie earlier this month.

A pyrrole molecule's centre consists of a "flat pentagram" of five atoms, four carbon and one nitrogen. Each of these atoms has an additional hydrogen atom attached, sticking out like spokes.

Following experiments performed by Barbara Lechner at the Cavendish Laboratory to determine the energy required for movement of pyrrole across a copper surface, the team discovered a discrepancy that led them down a 'quantum' road to an unusual discovery.

In previous work on simpler molecules, the scientists were able to accurately calculate the 'activation barrier' – the energy required to loosen a molecule's bond to a surface, allowing movement – using 'density functional theory', a method that treats the electrons which bind the atoms according to quantum mechanics but, crucially, deals with atomic nuclei using a 'classical' physics approach.

Surprisingly, with pyrrole the predicted 'activation barriers' were way out, with calculations "less than a third of the measured value". After much head scratching, puzzled scientists turned to a purely quantum phenomenon called 'zero-point energy'.

In classical physics, an object losing energy can continue to do so until it can be thought of as sitting perfectly still. In the quantum world, this is never the case: everything always retains some form of residual – even undetectable – energy, known as 'zero-point energy'.

While 'zero-point energy' is well known to be associated with motion of the atoms contained in molecules, it was previously believed that such tiny amounts of energy simply don't affect the molecule as a whole to any measurable extent, unless the molecule broke apart.

But now, the researchers have discovered that the "quantum nature" of the molecule's internal motion actually does affect the molecule as a whole as it moves across the surface, defying the 'classical' laws that it's simply too big to feel quantum effects.

'Zero-point energy' moving within a pyrrole molecule is unexpectedly sensitive to the exact site occupied by the molecule on the surface. In moving from one site to another, the 'activation energy' must include a sizeable contribution due to the change in the quantum 'zero-point energy'.

Scientists believe the effect is particularly noticeable in the case of pyrrole because the 'activation energy' needed for diffusion is particularly small, but that many other similar molecules ought to show the same kind of behavior.

"Understanding the nature of molecular diffusion on metal surfaces is of great current interest, due to efforts to manufacture two-dimensional networks of ring-like molecules for use in optical, electronic or spintronic devices," said Dr Stephen Jenkins, who heads up the Surface Science Group in Cambridge's Department of Chemistry.

"The balance between the activation energy and the energy barrier that sticks the molecules to the surface is critical in determining which networks are able to form under different conditions."

Stephen Jenkins | EurekAlert!
Further information:
http://www.cam.ac.uk

All articles from Life Sciences >>>

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 >>>