Potential 4-D imaging technique modeled by UNL physicists

December 21, 2010 By Tim Simons
A color JPEG image of a figure that illustrates an experiment modeled by Hua-Chieh Shao and Anthony Starace. It shows the 110-attosecond electron pulse sent through a beam of hydrogen atoms (green) excited by a laser (red).

(PhysOrg.com) -- A long-standing goal of science is to be able to understand how matter behaves at the atomic and subatomic level.

How electrons rearrange when atoms or molecules come together is the essence of chemistry, and the ability to manipulate those rearrangements is the goal of the emerging sphere of nanotechnology. A fuller understanding could lead to enormous scientific and technological breakthroughs.

Unfortunately, significant problems confront scientists and engineers in attacking the question. Not only are atoms and molecules very small, requiring highly specialized equipment to "see" them, everything at the happens very, very fast. For example, an electron goes around the nucleus of an atom once every 150 attoseconds -- that's around one 10 millionth of a billionth of a second, far too quick for the human eye or any existing equipment to detect.

Scientists have a good understanding for simple chemical combinations, but not for complex entities like . And nanotechnologists essentially operate in the blind in the sense that they are not yet able to watch while the nanostructures they construct are being assembled. They only know if they have succeeded after the fact.

Nothing exists to allow scientists and engineers to see those electronic processes, but University of Nebraska-Lincoln physics graduate student Hua-Chieh Shao and his adviser, Anthony Starace, have modeled a four-dimensional imaging technique that could lead to a breakthrough. They report their findings this week in the online edition of . Their paper will appear in the Dec. 31 print edition of the journal. The research was supported in part by funding from the National Science Foundation and the Nebraska Research Initiative.

Starace said he and Shao were intrigued by research that his UNL colleagues Herman Batelaan and Kees Uiterwaal were doing with Nobel laureate Ahmed Zewail of Cal Tech on what Zewail terms four-dimensional imaging -- imaging electronic processes in both space and time with very energetic, but extremely short, pulses of electrons.

"We got excited about this idea and decided to do what I think are among the first calculations, if not the first, to show what you would see," said Starace, University Professor and George Holmes Professor of Physics.

Deriving analytic formulas as far as possible and then writing computer programs to evaluate the formulas and analyze the results, Shao and Starace determined what would happen if electron pulses of 110 attoseconds were fired at targets excited by a laser field. Their first target was the hydrogen atom, with one proton and one electron. Their second target was the tritium molecule, a hydrogen isotope with one electron and two nuclei.

In both instances, they found patterns in the distribution of scattered electrons that could be used to track changes in the target charge distribution over time -- in other words, how the position of the electrons was changing.

"These are sort of benchmark results showing this new technology that Zewail has called four-dimensional imaging," Starace said "We've shown among the first results in a realistic calculation that one could see for both an atom and a molecule. We made some assumptions (in the tritium calculations), but it's a fairly realistic picture of how electrons move in molecules."

It remains for experimentalists to develop the technique.

"Herman Batelaan and Kees Uiterwaal are working in collaboration with Zewail to develop the short electron pulses and our newest faculty member, Martin Centurion, has been talking with us about what experiments he may be able to do that would provide evidence of time-dependent electron motion. He does experiments with short pulses of electrons, but much longer than the pulses which we considered here," Starace said.

"I hope this will give added incentive to pursue this technology because we've shown that it can provide information that no other technique can provide. So now it's up to experimentalists to develop the tools. Scientifically, there's nothing stopping the development of the tools except money and manpower, as usual."

Explore further: Study gives clues to increasing X-rays' power

Related Stories

Study gives clues to increasing X-rays' power

June 16, 2009

Three-dimensional, real-time X-ray images of patients could be closer to reality because of research recently completed by scientists at the University of Nebraska-Lincoln and a pair of Russian institutes.

Caltech scientists film photons with electrons

December 16, 2009

(PhysOrg.com) -- Techniques recently invented by researchers at the California Institute of Technology -- which allow the real-time, real-space visualization of fleeting changes in the structure of nanoscale matter -- have ...

Scientists track electrons in molecules

June 13, 2010

(PhysOrg.com) -- Physicists in Europe have successfully glimpsed the motion of electrons in molecules. The results are a major boon for the research world. Knowing how electrons move within molecules will facilitate observations ...

Prestigious award for the generation of attosecond pulses

May 23, 2006

Professor Ferenc Krausz, Director at Max Planck Institute of Quantum Optics, receives the 2006 IEEE/LEOS Quantum Electronics Award This award recognizes truly excellent and time-tested work in any of the fields of interest ...

Recommended for you

Complete design of a silicon quantum computer chip unveiled

December 15, 2017

Research teams all over the world are exploring different ways to design a working computing chip that can integrate quantum interactions. Now, UNSW engineers believe they have cracked the problem, reimagining the silicon ...

Single-photon detector can count to four

December 15, 2017

Engineers have shown that a widely used method of detecting single photons can also count the presence of at least four photons at a time. The researchers say this discovery will unlock new capabilities in physics labs working ...

Real-time observation of collective quantum modes

December 15, 2017

A cylindrical rod is rotationally symmetric - after any arbitrary rotation around its axis it always looks the same. If an increasingly large force is applied to it in the longitudinal direction, however, it will eventually ...

A shoe-box-sized chemical detector

December 15, 2017

A chemical sensor prototype developed at the University of Michigan will be able to detect "single-fingerprint quantities" of substances from a distance of more than 100 feet away, and its developers are working to shrink ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Dec 22, 2010
There is a great work done by G.Shpenkov and L.Kreidik!
http://shpenkov.janmax.com/books.asp" title="http://http://shpenkov.janmax.com/books.asp" rel="nofollow" target="_blank">http://shpenkov.j...ooks.asp
L.G. Kreidik and G.P. Shpenkov, Alternative Picture of the World, Vol. 1-3, Bydgoszcz-POLAND, 1996.
L.G. Kreidik and G.P. Shpenkov, Foundations of Physics; 13.644…Collected Papers, Bydgoszcz-POLAND,

1 / 5 (1) Dec 22, 2010
There is great work of G.Shpenkov L.Kreidik:

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.