Application of deep raman spectroscopy to detect ammonium nitrate concealed in color fabrics

Abstract

Detection of concealed Improvised Explosive Devices (IEDs) is a prerequisite for forensic and homeland security investigations. In this case, fabrics are common barriers for hidden explosives to be seen or detected. Deep Raman spectroscopy is a well-known detection method that provides detailed vibrational information about the depth profiling of Raman-active materials. In this research, a combination of space-resolved and time-resolved Raman techniques was successfully used to acquire high-quality ammonium nitrate Raman spectra concealed in white and brown synthetic fabric as a highly fluorescing barrier. The signal-to-background noise ratio was calculated in all the experiments. Concerning the result for white synthetic fabric, the optimum value was at 180 ns gate delay and 2 mm offset. These values were at 100 ns gate delay and 3 mm offset for brown synthetic fabrics. The role of retarded Raman photons in offset and gate delay variations was discussed too. As the results showed, implementing TR-SORS to identify the IEDs concealed in color fabrics caused the accelerated rejection of high fluorescence from the container surface and led to improved Raman signal.