German researchers have developed a method of screening for explosive liquids at airports.

The screening of liquids during airport security checks could be made possible in just one fifth of a second, using a method of spectroscopy developed in Germany.

German scientists published research in the journal Superconductor Science and Technology, which has revealed that the technique of Hilbert Spectroscopy could potentially end restrictions on liquids carried onto commercial airlines.

The group at the Forschungszentrum (Research Centre) Juelich in Germany use a very wide spectrum of light to identify either liquids that could be mixed to form an explosive, or that are already mixed.

Spectroscopy/spectrometry is often used in physical and analytical chemistry for the identification of substances through the spectrum emitted from or absorbed by them.

Currently, the unambiguous identification of liquids can be made by electromagnetic measurements of their dielectric functions in the frequency range of their main dispersions, but this frequency range, from a few GHz to a few THz, is not covered by any conventional spectroscopy.

Their new concept of liquid identification is based on the new Hilbert spectroscopy and high-Tc Josephson junctions, which can operate at the intermediate range from microwaves to THz frequencies.

A demonstration setup has been developed consisting of a polychromatic radiation source and a compact Hilbert spectrometer integrated in a Stirling cryocooler. Reflection polychromatic spectra of various bottled liquids have been measured at the spectral range of 15–300 GHz with total scanning time down to 0.2s and identification of liquids has been demonstrated.

Fast and reliable identification of liquids is also of great importance in the beverage industry, and in biology.

One of the report’s authors, Dr Divin, told the BBC, “[In] applications where you need high-speed operation – such as security screening – it should happen fast and in a “broadband” [way] to make it reliable with a low number of false alarms. Hilbert spectroscopy does that”.

Although further developments are necessary to refine the approach, the researchers are confident the technique can be applied to security screening – in such a way that the frequency of false alarms is low, and it does not disturb the normal flow of passengers through security checkpoints.

For more information, click here to read the journal article.