Diffuse Fresnel reflection spectroscopy of explosive RDX studied by THz time-domain spectroscopy

We report the measurement of the diffuse reflection spectrum of RDX by using THz time-domain spectroscopy. The absorption spectrum obtained from the diffuse Fresnel reflection measurement agrees with that from the transmission measurement. Two materials, polyethylene and flour that have no THz absorption fingerprints were also examined for comparison. When the RDX sample was covered with some optically opaque materials, the THz absorption at 0.82 THz was still identified by the diffuse reflection measurement. Our investigation shows that THz technique is capable of detecting the hidden RDX and related explosives in diffuse reflection geometry, which is well suited for standoff detection in real world.