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B. Zachhuber, G. Ramer, A. Hobro, B. Lendl:
"Stand-off Raman Spectroscopy of Explosives";
Vortrag: Security and Defence, Toulouse; 20.09.2010 - 23.09.2010; in: "Security and Defence 2010", (2010), ISBN: 978-0-8194-8357-7; 10 S.

We present our work on stand-off Raman detection of explosives and related compounds. Our system employs 532 or
355 nm laser excitation wavelengths, operating at 10 Hz with a 4.4 ns pulse length and variable pulse energy (maximum
180 mJ/pulse at 532 nm and 120 mJ/pulse at 355 nm). The Raman scattered light is collected by a co-axially aligned 6"
telescope and then transferred via a fiber optic cable and spectrograph to a fast gating iCCD camera capable of gating at
500 ps. We present results including the effect of different excitation wavelengths, showing that 355 nm excitation gives
rise to significantly stronger stand-off Raman signals compared to that of 532 nm. We also show the effect of appropriate
detector gating widths for discrimination of ambient light and the reduction of high background signals in the obtained
Raman spectra. Our system can be used to identify explosives and their precursors in both bulk and trace forms such as
RDX and PETN in the low mg range and TNT in the 700 μg range at a distance of 20 m, as well as detection of a 1% or
greater H2O2 solution at a distance of 6.3 m.