Complete spectroscopic picture of concealed explosives: Laser induced Raman versus infrared

There is a great advantage of any explosive detection technique which does not require direct physical contact with explosive material and also being suitable for standoff detection; such technique is Raman spectroscopy. This paper reports on tailored Raman with real-time and standoff detection capabilities of concealed explosives. It was possible to generate and spectrally resolve Stokes-Raman scattering for the three main explosive classes including: Nitro compounds, Nitramines, and Nitric esters. Induced Stokes-Raman spectra were compared to infrared absorptions using FTIR spectrometer. The two vibrational spectroscopic techniques were, in fact, complementary. Molecular vibrations with strong absorption in infrared (those involving strong change in dipole moments) were found to be weak emitter in Raman. The tailored-Raman offered instant detection, high sensitivity, and standoff detection capabilities; almost all explosive classes exhibited characteristic fingerprint spectra with intense peaks. Raman is one of the up and coming technologies for instantaneous detection of concealed explosives.