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Liquid Explosives Can Be Detected by New Laser Technique

One difficulty in detecting potentially dangerous materials like liquid explosives, as reported by Science & Technology Facilities Council's Rutherford Appleton Laboratory, is the wide variety of packaging in which air travelers can readily concealed these substances.

There is real concern about the use of liquid explosives by terrorists. We all know that this has led to current national and international security restrictions at airports and other places.

Dr. Pavel Matousek is the lead author of a scientific paper that reports on the successful application of a recently developed measurement technique using lasers. The technique is known as Spatially Offset Raman Spectroscopy (SORS). It was originally developed for medical and pharmaceutical applications as it can aid in diagnosis of diseases where subtle molecular details within tissue can provide indicators of health problems, for example, the non-invasive diagnosis of bone tissue or breast tissue.

SORS is a new revolutionary technique capable of investigating tissue beneath patients' skin and has been recently developed through an international multi-disciplinary collaborative project at Science & Technology Facilities Council (STFC). The Spatially Offset Raman Spectrometry technique allows for safe, non-invasive description of tissue layers at depths of several millimeters.

Raman spectrometry derives from Raman scattering or the Raman effect which is summarized as being the inelastic scattering of a photon. When light is scattered from an atom the photons that have the same frequency and wavelength as the atom's incident photons are elastically scattered. The small fraction of light photons that have a frequency different from the incident photon (usually lower) are scattered by excitation. These inelastic excitation scatterings of photons that have frequencies different from the atom from which light is scattered are Raman scatterings The effect was named for the Indian physicist Chandrasekhara Venkata Raman

The new Raman based SORS technique can be implemented by using a hand-held "probe." It generates spectrometry information relevant to liquids contained in transparent and diffuse plastic containers, which includes such containers that are made of colored materials.

This new and powerful technique that can detect hidden liquid explosives through common plastic containers and glass bottles has been demonstrated by scientists from STFC's Rutherford Appleton Laboratory, in Oxfordshire, UK. The research is reported in the American Chemical Society's journal, Analytical Chemistry.

"This work is a fine example of how fundamental scientific research can come up with solutions to practical problems that concern every one of us," says Professor Mike Dunne, the Director of the Central Laser Facility at the Rutherford Appleton Laboratory where the research has taken place.

Dr. Pavel Matousek, who is also the project team leader, commented, "As well as this exciting use in security, this technology is applicable to a wide range of problems. We are now planning to develop the technology commercially through a new spin-out company 'LiteThru Ltd', which will address areas such as pharmaceutical manufacture, anti-counterfeiting and medical diagnosis as well".

Since applications of this technology are not limited to security, it can be used for the detection of contaminated food products and beverages as well as in quality control of foods. Uses in pharmaceutical and chemical industries are also being tested.

The scientific paper by Dr. Charlotte Eliasson, Dr. Neil Macleod and Dr. Pavel Matousek in which the SORS laser method is reported is "Non-invasive Detection of Concealed Liquid Explosives using Raman Spectroscopy."

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