Raman spectroscopy, explosives identification

J.D. SantiUan, C.D. Brown and W. Jalenak, Advances in Raman spectroscopy for explosive identification in aviation security, Proc. SPIE-Int. Soc. Opt. Eng., 6540, 65400P/1-65400P/8 (2007). 

Optical spectroscopy Infrared (IR) and Raman spectroscopy can be used to make positive identifications however, it is not well suited to complex mixtures or detecting compounds at very low concentrations. Long-wavelength absorption spectroscopy such as millimeter wave are becoming attractive options as they provide the potential for very high specificity for volatilized explosives however, the sensitivity is not very high due to the low absorption cross sections at these wavelengths. 

The first review of laser Raman spectroscopy of explosives appeared in the late 1960s [30], A patent application for laser Raman applied to the remote identification of hazardous gases from explosives decomposition was filed a few years later [31],... 

Hodges C. M. and Akhavan J., The use of fourier transform Raman spectroscopy in the forensic identification of illicit drugs and explosives, Spectrochim. Act, 46A(2), 303-330, 1990. 

The fact that Raman measurements can usually be made through glass and plastic packaging, eliminating the need to prepare samples prior to analysis, makes Raman spectroscopy very attractive for forensic science. The availability of commercial portable instramentation and extended fiber optic probes makes Raman suitable for on-site forensic use, minimizing the risk of exposure of investigating personnel to potentially hazardous chemicals. Eor identification of explosives the SERS method has proved to be very useful. A tiny amount of explosive, diluted... 

According to our experience, Raman spectroscopy is the best tool for explosive materials identification. All known industrial and homemade explosive are characterized by specific Raman fingerprints under excitation by 532 nm (Fig. 7.7). The spontaneous Raman signal of explosives was measured at a distance of 30 m with a Nd YAG laser operating at 532 nm with an 18 mJ/pulse and 8-ns pulse duration... 

Raman spectroscopy has also been applied to the identification of different explosives. Most explosives, both nitro-containing (i.e. 2,4,6-trinitrotoluene (TNT)) and non-nitro-containing (i.e. TATP), produce high quality, low fluorescence Raman spectra. Some plastic explosives (i.e. Semtex) have some fluorescence originating from the binder materials but this can be overcome by use of anti-Stokes bands and Boltzmann correction of the data. 

---