Wideband Terahertz Spectroscopic Detection And Analysis Of Pyrotechnics

The detection and analysis of explosives is becoming more and more important as the current public concern about public safety is growing. The study of pyrotechnics is of great significance in the study of explosives because of pyrotechnics are the core components of various explosives. Although the thermal vapor pressure of the pyrotechnic is generally very low, it has the characteristics of low volatility and it is difficult to detect them by the content of the air in the air; The remnants of the pyrotechnic on the surface of the explosive object and its surroundings can persist for a considerable period of time so that the presence of the explosive can be detected by detecting the remnants of the pyrotechnic or its related compounds. We can use terahertz time-domain spectroscopy technology to obtain pyrotechnics Domain spectrum, spectrum and absorption spectra because of terahertz has high permeability, low energy and other characteristics, and many pyrotechnic s molecular rotation and vibration levels are located in the terahertz band, thereby establish the database. The molecular dynamics of the pyrotechnic was analyzed by Gaussian software, the vibration of the pyrotechnic molecules in each frequency band, the identification of the absorption peak and the reason of the absorption peak generated could be observed.In this paper, five different pyrotechnics were detected by terahertz time-domain spectroscopy. Then,five different pyrotechnics were analyzed by molecular theory, and then the vibrations of the molecules in each frequency band were observed by Gaussian View. The main research work is as follows:(1) In this paper, the structure of terahertz time domain spectroscopy (THz-TDS) system and its working principle are introduced in detail. Our labs have built-in transmission THz-TDS system, which measured the THz spectrum frequency can reach 3THz, its signal to noise ratio is very high and the experimental results are very ideal. At the same time, a comprehensive introduction to the THz-ABCD system structure and its working principle, the system measured by the frequency spectrum can reach 10THz,but above 6THz the signal to noise ratio is relatively low and the error is relatively large, The general selection of 6THz within the spectrum of experimental research.(2) In this paper, the THz-ABCD system was used to detect the water vapor with 15% humidity, and its broadband THz absorption spectrum was obtained. Its characteristic absorption peak was extracted to remove the suspicious absorption peak of the pyrotechnic agent. Five different kinds of pyrotechnics HMX(1,3,5,7tetranitroperhydro-1,3,5,7-tetrazocine)?RDX( 1,3,5-trinitroperhydro-1,3,5-triazine)?PETN(pentaery-thritotetranitrate) ?LLM-105 (2,6-diamino-3,5 -dinitrop-yrazine-1 -oxidated) ? TATB (1,3,5 -triamino-2,4,6-trinitrobenzene)were tested by THz-ABCD system. And their time domain spectra and frequency domain spectra were obtained. The broadband THz absorption spectra with frequency range of 0.5 ? 6.0THz were calculated.(3) The structures of HMX, RDX, PETN, LLM-105 and TATB were optimized by Gaussian09 software, and the calculation of the absorption frequency was carried out. The method chosen is density functional theory (DFT), the selected base group is 6-31G and 6-311G. The theoretical spectra of the absorption spectra were obtained by Gaussian View. At the same time, the molecular vibration and rotation at the absorption peak position were observed, and then the results were compared with the experimental results.