Nanostructures caught on film

A picture may be worth a thousand words, but a movie comprising several pictures can tell you about an object’s dynamics.

Scientists at Helmholtz-Zentrum Berlin für Materialien und Energie and at Technische Universität Berlin have developed a method to film processes at molecular levels often too minuscule and too fast to capture in action. After recording two pictures at such a short time interval, they are aiming to observe molecules and nano-structures in real time.

By capturing a molecule’s behavior at a crucial moment of a chemical reaction, a “molecular movie” could help researchers understand fundamental processes in the natural sciences. Most processes are only a few femtoseconds long.

Scientists took the green and red pictures of the Brandenburg Gate micromodel 50 fs apart. Courtesy of HZB/Stefan Eisebitt.

Although single femtosecond pictures using an ultrashort flash of light have been recorded, scientists have been unable to take a sequence of pictures in such rapid succession. Capturing the images on a detector has produced overlapped or washed-out pictures, and any attempts to swap or refresh the detectors between two images has taken too long, even if they could be done at the speed of light.

Despite these difficulties, the German researchers took ultrafast image sequences of objects mere micrometers in size, using pulses from the free-electron laser FLASH in Hamburg.

To descramble the information superimposed by the two subsequent x-ray pulses, they encoded both images simultaneously in a single x-ray hologram, obtaining the final image sequence after several steps.

An image of the central part of the recorded hologram of the Brandenburg Gate micro-model. Courtesy of HZB/Stefan Eisebitt.

Using their methodology, they recorded two pictures of a micromodel of the Brandenburg Gate, separated by only 50 fs. Short-wavelength x-rays revealed extremely small detail because the shorter the wavelength of light you use, the smaller the objects you can resolve.

Their work appeared Jan. 9, 2011, online in Nature Photonics (doi: 10.1038/ nphoton.2010.287).