Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Seeing molecules move in real-time

23.03.2009
Ultrafast lasers instantaneously track a molecular twist in progress

“Watching chemical reactions in real-time has long been a dream of chemists,” says Tahei Tahara of RIKEN’s Advanced Science Institute in Wako. “To reach a correct understanding of chemical reactions, this ‘watching’ is crucial.”

Tracking atoms in chemical reactions has previously seemed unrealistic, because the nuclei move so fast—movements can be complete within 1 picosecond (10-12 second). However, thanks to Tahara, scientists are awakening to a reality where an atom can be followed along a three-dimensional path.

In 2003, Tahara and his colleagues applied the technique known as impulsive stimulated Raman spectroscopy to measure short-lived, excited-state molecules for the first time (1). Using this method, the researchers initiated a chemical reaction by exciting electrons. Then, they induced the entire molecule to vibrate using 10-femtosecond (10-14 second) lasers—which emit light faster than nuclei move. Finally, using a third laser pulse, they measured how these atoms vibrated as the reaction progressed.

Now Tahara and a team of international and Japanese scientists have directly observed how an organic molecule named stilbene rearranges its structure (2). The initial isomer, called cis-stilbene, has two benzene rings positioned close together and connected by a carbon double bond. When excited by light, this molecule twists and rearranges to trans-stilbene, such that the benzene rings end up far apart.

Scientists have long believed that stilbene rearrangement is accomplished by the large motion of the benzene rings. Watching this reaction with Tahara’s spectroscopic method, however, revealed that the molecule changes geometry using a completely different mechanism.

“With excitation, the central carbon double bond is weakened,” explains Tahara. Then, hydrogen atoms attached to the carbon double bond moved in opposite directions, initiating a twisting motion that led to trans-stilbene. “That stilbene twisting is realized by hydrogen atom movement, [and] not by a large motion of benzene rings, was surprising to us,” says Tahara.

To visualize the three-dimensional molecular motion, the team combined experimental results with a high-level quantum-chemical calculation. The computation correlated the frequency changes observed in the experiment with particular molecular movements—and helped identify the exact twisting mechanism.

Tahara and his team’s advanced spectroscopy provides reliable checkpoints to gauge the accuracy of theoretical calculations—a combined approach that will be useful in visualizing other molecular systems.

Tahara says he doesn’t know how conceivable it is to control chemical reactions by light. “Nevertheless, I would like to try it on the basis of solid understanding of the potential energy of reactive molecules, which is obtainable by this type of study.”

References:

1. Fujiyoshi, S., Takeuchi, S. & Tahara, T. Time-resolved impulsive stimulated Raman scattering from excited-state polyatomic molecules in solution. Journal of Physical Chemistry A 107, 494–500 (2003).

2. Takeuchi, S., Ruhman, S., Tsuneda, T., Chiba M., Taketsugu T. & Tahara, T. Spectroscopic tracking of structural evolution in ultrafast stilbene photoisomerization. Science 322, 1073–1077 (2008).

The corresponding author for this highlight is based at the RIKEN Molecular Spectroscopy Laboratory

Saeko Okada | Research asia research news
Further information:
http://www.researchsea.com
http://www.rikenresearch.riken.jp/research/667/

More articles from Life Sciences:

nachricht Repairing damaged hearts with self-healing heart cells
22.08.2017 | National University Health System

nachricht Biochemical 'fingerprints' reveal diabetes progression
22.08.2017 | Umea University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>