Ultra violet decomposition of surface adsorbed explosives investigated with infrared standoff spectroscopy

Here we present a standoff spectroscopic technique where ultraviolet (UV) and infrared radiations are used in tandem to identify explosive residues on a surface 8 m away. Instead of analyzing byproducts, UV illumination induced changes in the adsorbates are investigated. The UV radiation is used to photodecompose the surface adsorbed explosive residues while the surface is probed with a tunable infrared quantum cascade laser. IR spectral changes generated after UV exposure are compared to the IR spectra before UV exposure to yield a signature similar to traditional transmittance plots for each explosive residue tested. Spectral variation the explosive compounds can be clearly identified with a surface concentration of 700 ng/cm ².