(Chem) Kinetics(Dynamics): The Speediest Ever Motion
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#1: (Chem) Kinetics(Dynamics): The Speediest Ever Motion Author: adediosLocation: Angel C. de Dios PostPosted: Fri Mar 03, 2006 12:50 pm

Source: Imperial College London

Posted: March 3, 2006

Scientists Capture The Speediest Ever Motion In A Molecule

The fastest ever observations of protons moving within a molecule open a new window on fundamental processes in chemistry and biology, researchers report in the journal Science.

Their capturing of the movements of the lightest and therefore speediest components of a molecule will allow scientists to study molecular behaviour previously too fast to be detected. It gives a new in-depth understanding of how molecules behave in chemical processes, providing opportunities for greater study and control of molecules, including the organic molecules that are the building blocks of life.

The high speed at which protons can travel during chemical reactions means their motion needs to be measured in units of time called 'attoseconds', with one attosecond equating to one billion-billionth of a second. The team's observation of proton motion with an accuracy of 100 attoseconds in hydrogen and methane molecules is the fastest ever recorded. Dr John Tisch of Imperial College London says:

"Slicing up a second into intervals as miniscule as 100 attoseconds, as our new technique enables us to do, is extremely hard to conceptualise. It's like chopping up the 630 million kilometres from here to Jupiter into pieces as wide as a human hair."

Professor Jon Marangos, Director of the Blackett Laboratory Laser Consortium at Imperial, says this new technique means scientists will now be able to measure and control the ultra-fast dynamics of molecules. He says:

"Control of this kind underpins an array of future technologies, such as control of chemical reactions, quantum computing and high brightness x-ray light sources for material processing. We now have a much clearer insight into what is happening within molecules and this allows us to carry out more stringent testing of theories of molecular structure and motion. This is likely to lead to improved methods of molecular synthesis and the nano-fabrication of a new generation of materials."

Lead author Dr Sarah Baker of Imperial College believes that the technique is also exciting because of its experimental simplicity. She says:

"We are very excited by these results, not only because we have 'watched' motion occurring faster than was previously possible, but because we have achieved this using a compact and simple technique that will make such study accessible to scientists around the world."

To make this breakthrough, scientists used a specially built laser system capable of producing extremely brief pulses of light. This pulsed light has an oscillating electrical field that exerts a powerful force on the electrons surrounding the protons, repeatedly tearing them from the molecule and driving them back into it.

This process causes the electrons to carry a large amount of energy, which they release as an x-ray photon before returning to their original state. How bright this x-ray is depends on how far the protons move in the time between the electrons' removal and return. The further the proton moves, the lower the intensity of the x-ray, allowing the team to measure how far a proton has moved during the electron oscillation period.


Questions to explore further this topic:

Activities on Dynamics


Newton's Law


Force Diagrams


Videos on Earth's dynamics


What is dynamics?


What is kinetics?


Molecular Dynamics

Surface Dynamics

Biomolecular Dynamics

Climate Dynamics

Fluid Dynamics

Soil Dynamics

Dynamics of Volcanic Eruptions

Solar Dynamics

Dynamics in Biology

What is diffusion?




Last edited by adedios on Sat Jan 27, 2007 3:59 pm; edited 2 times in total

#2: Earth's turbulence stirs things up slower than expected Author: adediosLocation: Angel C. de Dios PostPosted: Fri Mar 03, 2006 5:02 pm
Cornell University News Service
3 March 2006

Earth's turbulence stirs things up slower than expected

In a simple world rivers would flow in straight lines, every airplane ride would be smooth, and we would know the daily weather 10 years into the future. But the world is not simple -- it is turbulent.

That's good news, since turbulence helps drive natural processes essential for life. Unfortunately it also means we are never 100 percent sure it won't rain on Saturday.

"Turbulence is the last major unsolved problem of classical physics," explains Eberhard Bodenschatz, professor of physics who studies turbulence with his research group at Cornell and the Max Planck Institute (MPI) for Dynamics and Self-Organization, Germany.

The group recently moved closer to a solution by measuring how two tiny polystyrene spheres in turbulent water separate based on how far apart they initially are from each other. The results were published in the Feb. 10 issue of Science.

The findings suggest that, for almost every turbulent flow on Earth, including violent volcanic eruptions, particles separate more slowly than expected. This discovery could help improve models of dispersion of pollutants and bioagents and even help explain how crustaceans find food, mates and predators by sensing odors in the ocean depths.

Turbulence occurs when a gas or fluid, like air or water, is pushed at high speeds or on large scales, and is characterized by chaotic, seemingly random, flow patterns. Because of its complexity, turbulence is very efficient at mixing: a solution of two liquids, such as cream and coffee, will mix much more quickly if the flow is turbulent than if it is not.

As a white-water rafter might toss a stick into rapids to observe its behavior before jumping in, physicists watch particles in turbulence to understand the flow. A key measurement is how quickly two particles will separate, or "pair dispersion."

In the 1920s, British scientist L.F. Richardson predicted that pair dispersion should grow quickly, as time multiplied by itself twice (time cubed), independent of the initial separation of the pair -- a statement known as the Richardson-Obukhov law. In the 1950s, Australian-born Cambridge mathematician G.K. Batchelor added the amendment that for short timescales, pair dispersion is not independent of initial separation and should grow more slowly, as time multiplied by itself (time squared).

Until recently, the difficulty of photographing tiny particles at high speeds made direct measurements of these predictions impossible.

"When we first planned these experiments, fast enough cameras didn't exist," said Cornell graduate student Nicholas Ouellette, a co-author of the Science article. The final experiment used three high-tech digital cameras able to record up to 27,000 pictures per second of several hundred polystyrene spheres simultaneously in 8 cubic inches of water. The diameter of the spheres was about one-fourth the thickness of a human hair -- a thickness needed because it matched the smallest eddies in the turbulent water.

The experiment showed that when the initial separation of the spheres is large relative to the turnover time of the eddies, they will obey Batchelor dispersion, independent of the turbulence's severity. However, if the initial separation is smaller, then the particles will only exhibit Batchelor dispersion initially before transitioning to behavior consistent with the Richardson-Obukhov law.

"Right now new technology -- like our fast cameras -- is making experiments possible that just 10 years ago were considered impossible. It's a very exciting time to be in the field," Ouellette said.

The other authors of the Science paper are Haitao Xu, Cornell and MPI for Dynamics and Self-Organization, lead author Mickal Bourgoin, Laboratoire des Écoulenments Géophysiques et Industriels, France, and Jacob Berg, Ris National Laboratory, Denmark.

Thomas Oberst is a science writer intern at the Cornell News Service.

#3: New JILA apparatus measures fast nanoscale motions Author: adediosLocation: Angel C. de Dios PostPosted: Sun Mar 18, 2007 7:04 am
National Institute of Standards and Technology (NIST)

New JILA apparatus measures fast nanoscale motions
16 March 2007

A new nanoscale apparatus developed at JILA—a tiny gold beam whose 40 million vibrations per second are measured by hopping electrons—offers the potential for a 500-fold increase in the speed of scanning tunneling microscopes (STM), perhaps paving the way for scientists to watch atoms vibrate in high definition in real time.

The new device measures the wiggling of the beam, or, more precisely, the space between it and an electrically conducting point just a single atom wide, based on the speed of electrons “tunneling” across the gap. The work is the first use of an “atomic point contact,” the business end of an STM, to sense a nanomechanical device oscillating at its “resonant” frequency, where it naturally vibrates like a tuning fork. JILA is a joint venture of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

Although the JILA technique, described in the March 2 issue of Physical Review Letters,* is not necessarily as precise as more complex and much colder methods of measuring very fast motions of ultra-small devices, it incorporates several innovative attributes. These include the ability to minimize unwanted random electronic “noise” as well as to measure the random shaking of the beam caused by back-action or recoil (similar to what happens when a gun is fired). This level of sensitivity is possible because the atomic point contact acts as an amplifier for these otherwise imperceptible factors, and the gold beam is tiny and floppy enough—just 100 nanometers (nm) thick, and 5.6 micrometers long by 220 nm wide—to respond to single electrons.

The new method involves bringing the sharp point within one nanometer of the gold beam. A current is applied through the point across the gap, until an increase in resistance indicates that electrons are “tunneling” across the gap (a phenomenon observed only at atomic dimensions). The size of the gap is then monitored based on variations in the current. The beam’s undulations were measured with tens to hundreds of times greater precision than a typical STM result. That’s because the oscillations are measured using microwave electronics, which are much faster than the audio frequency technology typically used with STMs, thus enabling greater precision. The microwave measurement technique could potentially be applied to STMs.

View clip in avi format at http://www.nist.gov/public_aff.....mmodel.avi

#4: Catching waves: Measuring self-assembly in action Author: adediosLocation: Angel C. de Dios PostPosted: Fri Jun 22, 2007 9:12 am
National Institute of Standards and Technology (NIST)
22 June 2007

Catching waves: Measuring self-assembly in action

By making careful observations of the growth of a layer of molecules as they gradually cover the surface of a small silicon rectangle, researchers from the National Institute of Standards and Technology (NIST) and North Carolina State University (NCSU) have gained basic insights into how self-propagating self-assembly wave fronts develop and have produced the first experimental verification of recently improved theoretical models of such systems. In addition, the researchers say, the results reported in this week’s Proceedings of the National Academy of Science* should be important to understanding self-propagating chemical reactions and ordering and self-assembly phenomena in situations involving confinement, such as thin films and the porous internal geometries of many materials, such as rocks and cement.

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