Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Using musical chords to analyze and illustrate hydrogen molecule's response to laser pulses

04.02.2008
For Kansas State University physics professor Uwe Thumm, confirmation of a theory about the behavior of small molecules became music to his ears -- literally. He and colleagues in Heidelberg, Germany, have shown how a hydrogen molecule responds to laser pulses by using the changing musical chord created by the molecule's vibrational motion.

Thumm is a member of K-State's J.R. Macdonald Laboratory, where he is among several researchers who work on the properties and behavior of atoms and small molecules.

For decades, researchers had used the Macdonald Laboratory to make atoms and molecules collide with particles. Thumm said much of what scientists know about atoms and molecules is based on such collision experiments. To predict and explain what happens in these collisions, a large group of experimental physicists works closely with Thumm and two other theorists. The theorists use computers, make models and crunch numbers with the hope of producing results that are compatible with what experiments show.

Thanks to improvements in laser technology, around 1999 the Macdonald Laboratory researchers realized that they could transfer a lot of their expertise in atomic collisions to study in detail what happens when atoms and molecules get irradiated by very intense laser light. The new laser systems in the laboratory offer some advantages over the big particle accelerators, Thumm said. The laser pulses offer more control and can be made so short that the researchers now routinely observe the motion of nuclei inside small molecules in time. In addition, the laser pulses' peak intensity is enormous and would equal all of the sun's light focused onto a small spot of the size of a postage stamp or smaller.

Motivated by these opportunities, Thumm and his colleagues became curious about figuring out what would happen if the smallest and simplest molecule, hydrogen, were exposed to such ultra short and intense laser pulses. Together with his postdoctoral collaborator Bernold Feuerstein, Thumm developed a model and did calculations to determine how laser pulses influence the motion of the two protons in the hydrogen molecule.

"The short answer is that the laser pulse either makes the molecules vibrate more violently or blows them apart," Thumm said. He said this wasn't surprising because in the hydrogen molecule, two protons are connected by two electrons that function like a spring. When hit with the laser pulses, the protons oscillate back and forth.

Although this model may be easy to imagine on a large scale, Thumm said particles behave differently at the quantum level. This means that determining the locations of these oscillating protons isn't easy. Thumm described determining the protons' movements after being hit with the laser like what happens if you drop a marble in a bathtub. Looking at the circular ripples of water in the center of the tub, it's pretty easy to tell where the marble was dropped in. But when those ripples bounce off the sides of the tub, the wave pattern changes shape, and it becomes harder to tell where the marble was dropped. The wave gets delocalized. Thumm said the same thing happens to the protons not in a matter of seconds, but in a matter of femtoseconds -- that's a billionth of a millionth of a second. After about 60 femtoseconds, it's impossible to tell where the protons are.

"You quickly loose track of what the distance between the two protons is," Thumm said." All you can say is that they have a certain likelihood of being at a certain distance. This is in agreement with the bathtub experiment: Seconds after the marble was dropped, you can't tell where exactly it plunged in."

But things work differently at the quantum level, and the researchers were surprised that about 600 femtoseconds after being hit with the laser, the distance between the protons again becomes well defined. "We call this a revival of the original motion of the protons," Thumm said. "It's not going to happen in the bathtub, but it happens at the quantum level."

Thumm and Feuerstein published their theoretical prediction in 2003. Thumm said that they were pleasantly surprised when experiments at the Max-Planck Institute in Heidelberg, Germany, in 2006 confirmed the revival described in their model. "The agreement between the new experiments and our model was almost perfect and exceeded our expectations," Thumm said.

Feuerstein had since moved to Heidelberg, where he and his group of researchers continued to collaborate with Thumm's group at K-State. Excited about the success of their model, they began to analyze the molecule's vibrational motion by breaking it down into its various frequencies. Each frequency being like a note in a chord, the frequencies told researchers how the protons were behaving. However, the frequency of these molecular vibrations is way above the audible range. The two researchers share an interest in music and had collaborated musically before. So when it came time to illustrate the revival, they decided the best way to do it was to scale the frequencies down to 1,000 Hertz, which is in the range at which the human ear hears best. "This way you can listen to the vibrations and hear the revival. In the same way sound is analyzed and decomposed, we decomposed the vibration with regard to the frequencies," Thumm said. Their result, a changing musical chord coupled with a movie illustrating the protons' vibrations can be heard and viewed at http://www.mpg.de/video/FilmundoAudio-KdM.wmv

Thumm said researchers hope to be able to do the same thing for more complex molecules like water or methane. Just as a C Major chord sounds different from a d minor chord, Thumm said other molecules also would have their own unique sound. Thumm and Feuerstein's most recent work was first published last fall in the Physical Review Letters. Their research was supported by the National Science Foundation, the U.S. Department of Energy and the Max-Planck Society. Thumm said such basic research supports the long-term goal of applying lasers to steer chemical reactions. The hope is to largely increase the efficiency of chemical reactions by enhancing desired reaction pathways with lasers, he said.

Uwe Thumm | EurekAlert!
Further information:
http://www.mpg.de/video/FilmundoAudio-KdM.wmv

More articles from Physics and Astronomy:

nachricht Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

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: 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

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | 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

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>