Vibrational spectroscopy standoff detection of explosives |
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Authors: | Leonardo C Pacheco-Londoño William Ortiz-Rivera Oliva M Primera-Pedrozo Samuel P Hernández-Rivera |
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Institution: | (1) Center for Chemical Sensors Development/ALERT DHS Center of Excellence for Explosives, Department of Chemistry, University of Puerto Rico-Mayagüez, PO Box 9019, Mayagüez, Puerto Rico, 00681-9019 |
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Abstract: | Standoff infrared and Raman spectroscopy (SIRS and SRS) detection systems were designed from commercial instrumentation and
successfully tested in remote detection of high explosives (HE). The SIRS system was configured by coupling a Fourier-transform
infrared interferometer to a gold mirror and detector. The SRS instrument was built by fiber coupling a spectrograph to a
reflective telescope. HE samples were detected on stainless steel surfaces as thin films (2–30 μg/cm2) for SIRS experiments and as particles (3–85 mg) for SRS measurements. Nitroaromatic HEs: TNT, DNT, RDX, C4, and Semtex-H
and TATP cyclic peroxide homemade explosive were used as targets. For the SIRS experiments, samples were placed at increasing
distances and an infrared beam was reflected from the stainless steel surfaces coated with the target chemicals at an angle
of ∼180° from surface normal. Stainless steel plates containing TNT and RDX were first characterized for coverage distribution
and surface concentration by reflection–absorption infrared spectroscopy. Targets were then placed at the standoff distance
and SIRS spectra were collected in active reflectance mode. Limits of detection (LOD) were determined for all distances measured
for the target HE. LOD values of 18 and 20 μg/cm2 were obtained for TNT and RDX, respectively, for the SIR longest standoff distance measured. For SRS experiments, as low
as 3 mg of TNT and RDX were detected at 7 m source–target distance employing 488 and 514.5 nm excitation wavelengths. The
first detection and quantification study of the important formulation C4 is reported. Detection limits as function of laser
powers and acquisition times and at a standoff distance of 7 m were obtained. |
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Keywords: | Standoff infrared detection Standoff Raman detection High explosives Explosive formulations |
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