Long-wave infrared scattering spectra and modeling of trace particles on surfaces for standoff detection.

We experimentally measure the scattered reflectance of particles deposited on smooth substrates with a mid-wave to long-wave supercontinuum source and a FTIR based sensor at 3.6 m. We measure the scattering return from sparse particles of 1,3,5-Trinitroperhydro-1,3,5-triazine, caffeine, and acetaminophen deposited on smooth aluminum, silicon, and glass substrates. We also measure mono-disperse 5.4, 10.8, and 19.4 μ m diameter polystyrene spheres deposited on aluminum. We demonstrate that spectra obtained using our supercontinuum FTIR sensor can be accurately simulated using a Bobbert–Vlieger model, and non-spherical particle spectra can be approximated by spherical results. The Bobbert–Vlieger model can then be used to create a library that can account for the trace chemical and underlying substrate for standoff chemical identification. [ABSTRACT FROM AUTHOR]