Stand-off detection of explosives vapors by resonance-enhanced Raman spectroscopy

Ida Johansson; Ema Ceco; Anneli Ehlerding; Henric Östmark

doi:10.1117/12.2017858

7 June 2013 Stand-off detection of explosives vapors by resonance-enhanced Raman spectroscopy

Ida Johansson, Ema Ceco, Anneli Ehlerding, Henric Östmark

Proceedings Volume 8709, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVIII; 87090N (2013) https://doi.org/10.1117/12.2017858
Event: SPIE Defense, Security, and Sensing, 2013, Baltimore, Maryland, United States

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.

Citation Download Citation

Ida Johansson, Ema Ceco, Anneli Ehlerding, and Henric Östmark "Stand-off detection of explosives vapors by resonance-enhanced Raman spectroscopy", Proc. SPIE 8709, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVIII, 87090N (7 June 2013); https://doi.org/10.1117/12.2017858

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