This release is available in German.
People like to keep a safe distance from explosive substances, but in order to analyze them, close contact is usually inevitable. At the Vienna University of Technology, a new method has now been developed to detect chemicals inside a container over a distance of more than a hundred meters. Laser light is scattered in a very specific way by different substances. Using this light, the contents of a nontransparent container can be analyzed without opening it.
Scattered Light as a "Chemical Fingerprint"
"The method we are using is Raman-spectroscopy", says Professor Bernhard Lendl (TU Vienna). The sample is irradiated with a laser beam. When the light is scattered by the molecules of the sample, it can change its energy. For example, the photons can transfer energy to the molecules by exciting molecular vibrations. This changes the wavelength of the light and thus its colour. Analyzing the colour spectrum of the scattered light, scientists can determine by what kind of molecules it must have been scattered.
Measuring over Great Distances with Highest Precision
"Until now, the sample had to be placed very close to the laser and the light detector for this kind of Raman-spectroscopy", says Bernard Zachhuber. Due to his technological advancements, measurements can now be made over long distances. "Among hundreds of millions of photons, only a few trigger a Raman-scattering process in the sample", says Bernhard Zachhuber. These scattered particles of light are scattered uniformly in all directions. Only a tiny fraction travel back to the light detector. From this very weak signal, as much information as possible has to be extracted. This can be done using a highly efficient telescope and extremely sensitive light detectors.
In this project (funded by the EU) the re
|Contact: Florian Aigner|
Vienna University of Technology