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THz diffuse reflectance spectra of selected explosives and related compounds

Diffuse reflectance spectrum (DRS) technique is extensively used in UV/visible and middle/near infrared for characterizing/analyzing powders and samples with rough surface. In this paper, we report on the DRS investigation of explosives & related compounds in the THz region, which is more difficult because of the limitations of far infrared sources, beam splitters and detectors. We also discussed the penetration depth and the sensitivity for this technique in the THz range. THz diffuse reflectance spectra (50-680 cm-1) were taken on a Bruker 66V/S FTIR spectrometer with a Specac diffuse reflectance accessory. A number of explosive and related compounds were investigated in both transmission and diffuse reflectance modes, and a good agreement between transmission and diffuse reflection spectra was demonstrated. Our experimental results show that DRS technique has advantages over transmission spectrum technique, such as better sensitivity and easier sample preparation. Therefore, the THz DRS has the potential for the standoff detection of explosives and related compounds in the real world applications.