Detection of Explosives using Pulsed Laser Fragmentation andMIRSpectroscopy

Abstract

Within the past years, an increasing number of optical techniques for the detection of harmful substances has been investigated on account of the threat of terroristic attacks. Optical technologies have the capability to overcome the problems of extensive sample preparation and long measurement cycles that are known from widely used detection techniques such as mass spectrometry and gas chromatography. The threat of bombings has also produced interest in standoff techniques — in addition to checkpoint applications for screening of persons. Even in this field, optical technologies are well suited: to date, Raman spectroscopy and laser‐induced breakdown spectroscopy (LIBS) seem to be the most promising technologies, but other optical methods are permanently developed. Particularly detection in the midinfrared (MIR) spectral region, providing selective fingerprints of molecules in the range from 3 to 11 µm, has experienced a renaissance with development of new laser sources, detectors, and spectroscopic techniques. In this paper, some comparatively new techniques for the detection of explosives in the MIR spectral range, relying on quantum cascade lasers (QCLs) and photoacoustic spectroscopy (PAS), are presented. Another emphasis is put on the indirect detection of explosives via characteristic decomposition products and their active generation with laser‐induced photodissociation techniques.

Support vector machine classification of volatile organic compounds based on narrow‐band spectroscopic data

“…Many technologies have been recalled to contribute to this direction, such as X-rays-based technologies (capable for bulk detection of a wide range of substances but cannot be used to screen persons) [1][2][3], magnetic portals (for metal detection), millimeter or terahertz wave imagers (capable also for bulk detection only) [4][5][6][7], ion mobility spectrometry (currently one of the most efficient for explosives, drugs, and hidden persons trace detection) [8][9][10][11], and CO 2 sensors (capable for hidden person detection but with low reliability operation) [12,13]. Finally, midinfrared (MIR) spectroscopic methods have been widely used to trace the occurrence of chemical compounds for various applications, such as food analysis, air quality assessment, forbidden substance detection, and border security [14][15][16][17][18][19][20][21][22]. More specifically, MIR spectroscopy technology based on photoacoustic detection (MIRPAS) [23,24] appears as a new powerful tool to detect a very wide range of volatile organic compounds (VOCs) associated with the security agents of interest [25].…”