Instant identification of explosive material: Laser induced photoacoustic spectroscopy versus fourier transform infrared

Terrorism by means of explosive materials has become a serious threat. Instant identification of common explosive material is an urgent demand. Even though FTIR spectroscopy can offer signature based on chemical structure; this technology requires sample handling and processing. On the other hand, laser induced photoacoustic spectroscopy (LIPAS) can offer outstanding characteristic signatures. Common commercial explosive materials were subjected to LIPAS analysis via stimulating the tested material with pulsed Q-switched Nd:YAG laser. Generated photoacoustic signature was captured and processed via high response piezoelectric transducer and novel digital signal processing algorithm designed for time and frequency domain analysis respectively. Each explosive material demonstrated characteristic absorption coefficient as well as frequency response. The main finding of this study is that phase-resolved domain analysis offered an outstanding signature. This phase-shift signature is candidate for data-base operation mode. LIPAS offered superior identification signatures compared with FTIR spectroscopy with the advantages of standoff detection capabilities.