Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Movement of pyrrole molecules defy 'classical' physics

Abstract:
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.

Movement of pyrrole molecules defy 'classical' physics

Cambridge, UK | Posted on April 28th, 2013

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."

Credits:

Stephen Jenkins is head of the Chemistry Department's Surface Science Group; Marco Sacchi is the post-doc in that group who did the calculations.

Bill Allison and John Ellis lead the Surface Science section of the Surfaces, Microstructure and Fracture Group at the Cavendish; Holly Hedgeland was a post-doc in that group, who started a lot of the experimental work on diffusion of aromatic molecules; Barbara Lechner was the student who took the lead on the experimental work for this specific system.

Jane Hinch is a collaborator from Rutgers University, involved in the experimental work and its interpretation

####

For more information, please click here

Contacts:
Stephen Jenkins

44-012-233-36502

Copyright © University of Cambridge

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

Physics

X-ray photoelectron spectroscopy under real ambient pressure conditions June 28th, 2017

News and information

X-ray photoelectron spectroscopy under real ambient pressure conditions June 28th, 2017

Nanometrics to Participate in the 9th Annual CEO Investor Summit 2017: Accredited investor and publishing research analyst event held concurrently with SEMICON West and Intersolar 2017 in San Francisco June 27th, 2017

NMRC, University of Nottingham chooses the Quorum Q150 coater for its reliable and reproducible film thickness when coating samples with iridium June 27th, 2017

Picosunís ALD solutions enable novel high-speed memories June 27th, 2017

Spintronics

Smart multi-layered magnetic material acts as an electric switch: New study reveals characteristic of islands of magnetic metals between vacuum gaps, displaying tunnelling electric current March 1st, 2017

First experimental proof of a 70 year old physics theory: First observation of magnetic phase transition in 2-D materials, as predicted by the Nobel winner Onsager in 1943 January 6th, 2017

Investigations of the skyrmion Hall effect reveal surprising results: One step further towards the application of skyrmions in spintronic devices December 28th, 2016

Electron highway inside crystal December 12th, 2016

Discoveries

X-ray photoelectron spectroscopy under real ambient pressure conditions June 28th, 2017

Physicists make quantum leap in understanding life's nanoscale machinery June 27th, 2017

Picosunís ALD solutions enable novel high-speed memories June 27th, 2017

Atomic imperfections move quantum communication network closer to reality June 25th, 2017

Announcements

X-ray photoelectron spectroscopy under real ambient pressure conditions June 28th, 2017

Nanometrics to Participate in the 9th Annual CEO Investor Summit 2017: Accredited investor and publishing research analyst event held concurrently with SEMICON West and Intersolar 2017 in San Francisco June 27th, 2017

NMRC, University of Nottingham chooses the Quorum Q150 coater for its reliable and reproducible film thickness when coating samples with iridium June 27th, 2017

Picosunís ALD solutions enable novel high-speed memories June 27th, 2017

Photonics/Optics/Lasers

Rice U. chemists create 3-D printed graphene foam June 22nd, 2017

New carbon nitride material coupled with ruthenium enhances visible-light CO2 reduction in water June 15th, 2017

Changing the color of laser light on the femtosecond time scale: How BiCoO3 achieves second harmonic generation June 14th, 2017

Learning with light: New system allows optical ďdeep learningĒ: Neural networks could be implemented more quickly using new photonic technology June 12th, 2017

Quantum nanoscience

Physicists make quantum leap in understanding life's nanoscale machinery June 27th, 2017

Atomic imperfections move quantum communication network closer to reality June 25th, 2017

Oxford Instruments congratulates Lancaster University for inaugurating the IsoLab, built for studying quantum systems June 20th, 2017

In atomic propellers, quantum phenomena can mimic everyday physics June 1st, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project