FLASH Illuminates Nano-World

Photo: The microstrusture detected with a laser puls

Using the soft X-ray free-electron laser FLASH at DESY in Hamburg, an international team of scientists achieved a world first by taking a high-resolution diffraction image of a non-crystalline sample with a single extremely short and intense laser shot.

In the FLASH experiment, the researchers directed a very intense free-electron laser pulse of 32 nanometers wavelength and only 25 femtoseconds duration at a test sample, a thin membrane into which 3-micrometer-wide patterns had been cut. The energy of the laser pulse heated the sample up to around 60,000 Kelvin, causing it to vaporize. However, the international team of scientists was able to record an interpretable diffraction pattern before the sample was destroyed.

The experiment suggests that in the near future images from nano-particles and even large individual macromolecules like viruses or cells may be obtained using a single ultra-short high-intensity laser pulse with an application called "flash diffractive imaging".

"The experimental principle that was verified at DESY's new FLASH free-electron laser promises to revolutionize structure research in many areas of science, including the life sciences, where ever very high spatial and temporal resolution is required," says Professor Jochen Schneider, DESY research director and co-author of the paper. "As the only soft X-ray laser providing extremely bright coherent pulses of just 25 femtoseconds duration, FLASH is the world's first radiation source to permit this and other proof-of-principle experiments.”

In order to take images from large molecules with atomic resolution, such experiments will have to be carried out using radiation of even shorter wavelengths, i.e. hard X-rays such as the ones that will be produced from 2009 on by LCLS in Stanford, or by the European X-ray laser XFEL in Hamburg, due to take up operation in 2013. Since the method demonstrated at FLASH does not require any image-forming optic, it can be extended to these hard X-ray regimes, for which no lenses currently exists.

COMPAMED.de; Source: Deutsches Elektronen-Synchrotron DESY