Mid-Infrared Vibrational Spectroscopy Standoff Detection of Highly Energetic Materials: New Developments

摘要: Infrared (IR) spectroscopy has played an important role in the characterization of highly energetic materials. IR spectroscopy contributions in the area of laboratory-based detection and characterization of highly energetic materials (HEMs) were reviewed by Steinfeld and Wormhoudt (1) in 1998 and later updated by Moore in 2004 (2) and 2007 (3). As discussed in these reviews, solid and liquid phase IR reference spectra of HEMs and propellants (1) and cyclic organic peroxides (4) are available for characterization and identification purposes. Remote gas phase sensing has been limited to high vapor pressure chemical agents, toxic industrial compounds (TICs), and high-vapor-pressure cyclic organic peroxides (for example, TATP)(5, 6). Most HEM contain nitro (-NO2) groups, whose vibrational signatures are very characteristic. Beal and Brill (7) provided a comprehensive treatise on the behavior of the vibrational spectra of the-NO2 groups in more than 50 energetic compounds. They noted that the scissor vibrations (842–846 cm-1) are remarkably insensitive to differences in the local chemical environment and therefore could be used as detection tags. Similarly, the presence of nitro group bands evidenced by signatures at 760 cm-1,~ 1350 cm-1 (symmetric NO2 stretch), and~ 1600 cm-1 (asymmetric NO2 stretch) can be used as markers within nitro compounds. These signatures can be used universally to detect these compounds from a distance. The merits and challenges for such a technique include a. Remote: the technique should be capable of detecting HEM and HEM at long distances (ie, tens to hundreds of meters). b. Universal: the …