Trace detection of explosive and their derivatives in stand-off mode using time gated Raman spectroscopy

Trace detection is utmost important for detection of concealed explosive materials in form of IEDs. Surfaces of suspicious objects may be scanned for contamination of explosives. Sensitivity and selectivity are two main concerns in field of explosive detection. Raman spectroscopy provides remarkable selectivity. Time-gated Raman spectroscopy also has potential of providing sensitivity for trace detection. In present study, time-gated Raman spectroscopy investigated for detection of ppm level concentration of explosives. To achieve better sensitivity, various parameters of the experimental set-up like gain of intensifier, number of pulse accumulated and pulse energy of laser were optimised. The trend of change in intensity of Raman scattering (background subtracted) was observed by varying values of these above mentioned parameters. Followed by optimization of these parameters for better sensitivity, Raman spectra of RDX samples at lower concentrations (prepared by mixing RDX with KBr) were recorded. The corrected intensity increased in linear fashion with increase in gain of intensifier, number of pulses accumulated and pulse energy. After that, Raman spectra of RDX were recorded from a stand-off distance of 5 m in backscattered mode with concentrations down to 100 ppm.