Raman Spectroscopy for Detecting Traces of Explosives at Security Checkpoints

Kurzfassung

Remote detection of hazardous materials is of great interest as it allows for real-time threat detection without putting people in harm’s way. It is thus highly important to develop new chemically selective and sensitive methods to detect such materials from afar. There are a number of techniques, such as for example infrared spectroscopy, laser-induced fluorescence, and Raman spectroscopy [1-3], that can be used for remote detection of explosives. Especially UV Raman spectroscopy is a very promising technique as it is highly selective and far more sensitive than conventional Raman spectroscopy using visible or near-infrared light sources. Additional advantages of using UV light as the excitation source are the reduced interference with the fluorescence background and a possible resonance enhancement when the excitation wavelength approaches electronic transitions in the sample [2, 4]. In order to monitor for hazardous materials at e.g. security checkpoints, the spectroscopic unit has to be combined with an optical tracing unit to locate the position of the sample and align the optics toward the sample. In such a scenario, variations in target distance and the angle of incidence have to be considered. Other important parameters influencing the systems detection sensitivity include interfering signals from background materials and overall material coverage, as well as penetration depth and energy density of the laser. Here, we present a concept of using a UV laser for remote Raman scattering detection of trace amounts of explosive materials at security checkpoints. The influence of the above-mentioned parameters on UV explosives Raman spectra recorded with our system will be evaluated. REFERENCES [1] Lu, T., et al., Simultaneous determination of multiple components in explosives using ultraviolet spectrophotometry and a partial least squares method. RSC Advances, (2015). 5 (17): p. 13021-13027. [2] Ehlerding, A., et al., Resonance-Enhanced Raman Spectroscopy on Explosives Vapor at Standoff Distances. International Journal of Spectroscopy, (2012). 2012: p. 1-9. [3] Harmon, R.S., et al., Stand-off detection of explosive particles by imaging Raman spectroscopy. Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVI, (2011). [4] Nagli, L., et al., Absolute Raman cross-sections of some explosives: Trend to UV. Optical Materials, (2008). 30 (11): p. 1747-1754.