Abstract
Deep ultraviolet Raman spectroscopy measurements have been performed at the German Aerospace Center (DLR) with the aim of detecting traces (μg range) of explosive precursors. In this study, a backscattering Raman system was setup and optimized to detect urea, sodium perchlorate, ammonium nitrate, and sodium nitrate at a 60-cm short-range remote detection. The sample was tested at 264-nm ultraviolet laser excitation wavelength to experimentally observe any possible trace over textiles samples. For each colored sample textile, Raman spectra were acquired and no background fluorescence interference was observed at this laser excitation wavelength. Detection limits and system sensitivity with an acquisition time up to 3 s for microgram traces are presented.
Highlights
Remote laser-based techniques are useful to detect harmful substances without requiring direct contact from the operator
The aim of this study is to find the detection limits to develop a screening device for civil applications
Explosive precursors samples were prepared over different colored textile materials: urea (Fig. 2), sodium perchlorate (Fig. 3), ammonium nitrate (Fig. 4), and sodium nitrate (Fig. 5)
Summary
Remote laser-based techniques are useful to detect harmful substances (such as vapors and particles from explosives or surface traces such as a fingerprint residue) without requiring direct contact from the operator. A potential warning at a safe distance from the identification site is wanted to both save the life of the personnel investigating a contaminated area and avoid directly damaging the detection required equipment.[1] Among many available laser-based techniques, Raman spectroscopy is a powerful tool to detect and uniquely identify unknown substances. It is non-destructive and highly selective[2,3,4,5,6] while other techniques such as infrared spectroscopy suffers more on the background surface (surface reflectivity and roughness) and sample size (thickness), which affects peak positions and intensities,[7] or laser-induced fluorescence, which is highly sensitive but poorly selective.[7] Spectroscopic detection of explosive traces and their precursors is a very important topic for homeland security applications to reduce the threat of improvised explosive devices (IED). For resonant Raman scattering, the scattered radiation carrying the signal information is inversely proportional to the forth power of the incident laser radiation wavelength, Optical Engineering
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