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Proceedings Paper

Stand-off detection of explosives vapors by resonance-enhanced Raman spectroscopy
Author(s): Ida Johansson; Ema Ceco; Anneli Ehlerding; Henric Östmark
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Paper Abstract

This paper describes a system for stand-off vapor detection based on Resonant Raman spectroscopy, RRS. The system is a step towards a RRS LIDAR (Light Detection And Ranging) system, capable of detecting vapors from explosives and explosives precursors at long distances. The current system was used to detect the vapor of nitromethane and mononitrotoluene outdoors in the open air, at a stand-off distance of 11–13 meters. Also, the signal dependence upon irradiation wavelength and sample concentration was studied in controlled laboratory conditions. A tunable Optical Parametric Oscillator pumped by an Nd:YAG laser, with a pulse length of 6 ns, was operated in the UV range of interest, 210–400 nm, illuminating the sample vapor. The backscattered Raman signal was collected by a telescope and a roundto- slit optical fiber was used to transmit collected light to the spectrometer with minimum losses. A gated intensified charge-coupled device (ICCD) registered the spectra. The nitromethane cross section was resonance enhanced more than a factor 30 700, when measured at 220 nm, compared to the 532 nm value. The results show that a decrease in concentration can have a positive effect on the sensitivity of the system, due to a decrease in absorption and selfabsorption in the sample.

Paper Details

Date Published: 7 June 2013
PDF: 10 pages
Proc. SPIE 8709, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVIII, 87090N (7 June 2013); doi: 10.1117/12.2017858
Show Author Affiliations
Ida Johansson, Swedish Defence Research Agency (Sweden)
Ema Ceco, Swedish Defence Research Agency (Sweden)
Anneli Ehlerding, Swedish Defence Research Agency (Sweden)
Henric Östmark, Swedish Defence Research Agency (Sweden)

Published in SPIE Proceedings Vol. 8709:
Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVIII
J. Thomas Broach; Jason C. Isaacs, Editor(s)

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