Search

ResonanceRaman cross sections of common explosives have been measuredby use of excitation wavelengths in the deep-UV from 229 to 262 nm.These measurements were performed both in solution and in the nativesolid state for comparison. While measurements of UV Raman cross sectionsin solution with an internal standard are straightforward and commonlyfound in the literature, measurements on the solid phase are rare.This is due to the difficulty in preparing a solid sample in whichthe molecules of the internal standard and absorbing analyte/explosiveexperience the same laser intensity. This requires producing solidsamples that are mixtures of strongly absorbing explosives and aninternal standard transparent at the UV wavelengths used. For thesolid-state measurements, it is necessary to use nanostructured mixturesof the explosive and the internal standard in order to avoid thisbias due to the strong UV absorption of the explosive. In this studywe used a facile spray-drying technique where the analyte of interestwas codeposited with the nonresonant standard onto an aluminum-coatedmicroscope slide. The generated resonance enhancement profiles andquantitative UV–vis absorption spectra were then used to plotthe relative Raman return as a function of excitation wavelength andparticle size. [ABSTRACT FROM AUTHOR]

Raman cross-sections of explosives in solution and in the solid state have been measured using visible and near-infrared excitation via secondary calibration. These measurements are valuable for both fundamental scientific purposes and applications in the standoff detection of explosives. The explosive compounds RDX, HMX, TNT, 2,4-DNT, 2,6-DNT, and ammonium nitrate were measured using discrete excitation wavelengths ranging from 532 nm to 785 nm. A comparison of the spectral features and cross-sections between the solid state and solution was performed. Comparison is also made to cross-sections measured with deep ultraviolet excitation. [ABSTRACT FROM AUTHOR]

In 2010, the U.S. Army initiated a program through the Edgewood Chemical Biological Center to identify viable spectroscopic signatures of explosives and initiate environmental persistence, fate, and transport studies for trace residues. These studies were ultimately designed to integrate these signatures into algorithms and experimentally evaluate sensor performance for explosives and precursor materials in existing chemical point and standoff detection systems. Accurate and validated optical cross sections and signatures are critical in benchmarking spectroscopic-based sensors. This program has provided important information for the scientists and engineers currently developing trace-detection solutions to the homemade explosive problem. With this information, the sensitivity of spectroscopic methods for explosives detection can now be quantitatively evaluated before the sensor is deployed and tested. [ABSTRACT FROM AUTHOR]