Scattering spectra from trace particles actively illuminated by a mid-infrared supercontinuum FTIR sensor

We measure and simulate the diffuse scattering return from sparse particles of RDX, caffeine, and acetaminophen deposited on substrates consisting of smooth aluminum, silicon, and glass substrates at a distance of 3.6 m using a mid-infrared supercontinuum FTIR sensor. The measured spectra show that molecular fingerprint regime contains reflectance peaks that can be used for chemical identification and the mid-wave infrared provides information for target orientation. Furthermore, we demonstrate that spectra obtained using our supercontinuum FTIR sensor can be accurately simulated using a Bobbert-Vlieger model. The Bobbert-Vlieger model can then be used to create a library that can account for the trace chemical, underlying substrate, and target orientation, for stand-off chemical identification.