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3 June 2011 Multiple-excitation-wavelength resonance-Raman explosives detection
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Deep-ultraviolet resonance Raman spectroscopy (DUVRRS) is a potential candidate for stand-off detection of explosives. A key challenge for stand-off sensors is to distinguish explosives, with high confidence, from a myriad of unknown background materials that may have interfering spectral peaks. To address this, we have investigated a new technique that simultaneously detects Raman spectra from multiple DUV excitation wavelengths. Due to complex interplay of resonant enhancement, self-absorption and laser penetration depth, significant intensity variation is observed between corresponding Raman bands with different excitation wavelengths. These variations with excitation wavelength provide a unique signature that complements the traditional Raman signature to improve specificity relative to singleexcitation- wavelength techniques. We have measured these signatures for a wide range of explosives using amplitudecalibrated Raman spectra, obtained sequentially by tuning a frequency-doubled Argon laser to 229, 238, 244 and 248 nm. For nearly all explosives, these signatures are found to be highly specific. An algorithm is developed to quantify the specificity of this technique. To establish the feasibility of this approach, a multi-wavelength DUV source, based on Nd:YAG harmonics and hydrogen Raman shifting, and a compact, high throughput DUV spectrometer, capable of simultaneous detection of Raman spectra in multiple spectral windows, are being investigated experimentally.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Balakishore Yellampelle, Mikhail Sluch, Sanford Asher, and Brian Lemoff "Multiple-excitation-wavelength resonance-Raman explosives detection", Proc. SPIE 8018, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XII, 801819 (3 June 2011);

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