A comprehensive understanding of the complex physical and chemical process involved in the dissociation process of energetic materials is essential for laser initiation. In this paper, experimental investigations were carried on to reveal the dissociation mechanism of 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) under 1064nm excitation. The positive and negative ions produced in the laser-induced dissociation processes were detected by a time of flight mass spectrometer (TOFMS) in vacuum (4×10-4 Pa). By analyzing the molecular structure of HNS and mass to charge ratio (m/z), possible attributions of different ions were obtained. For the negative ions, the dominant peak appeared at m/z=26, 42, 50, 74, 100 and 136, which corresponded to CN, CH2N2/C2H2O/CNO, CHCCHC, C6H2, C6H2CN and C6H2ONO2. For the positive ions, the main peaks could be found at m/z= 24, 28, and 40, these peaks could be ascribed to C2, CO/N2/CH2N and CH2CN. The intensity of the ion fragments increased gradually with the increasing of laser fluence. The relationship between the ion intensity and the delay time was also revealed. The results might give some help for the further understanding of the laser initiation process of HNS.
2, 4, 6-Trinitrotoluene (TNT) belongs to the group of aromatic nitro compounds which have extended use in industrial applications, in particular as explosives or additives to explosives. Understanding the initial step of laser induced decomposition of common explosives is important to the reliability and safety of laser initiators and firing systems. Lasers coupled with mass spectrometer find wide application in photochemical studies for identification of different ions formed due to photoexcitation/ionization of molecules by laser. In this paper, a pulsed Nd: YAG (15ns, 532nm) laser was used for ionizating the condensed TNT sample, and the ions produced in the ionization process were detected by a time of flight mass spectrometer (TOFMS). The influence of laser fluence and the delay time to the decomposition was also studied. According to the assignment of both positive and negative ions, possible laser induced dissociation pathways were proposed. The results may tell much about the initiation process and the chemical reaction that may occur in TNT when exposed to laser pulse.
A Q-switched Nd: YAG laser (with a wavelength of 532 nm and a pulse width of 15 ns) was used to ablate hexahydrol, 3,5-trinitro-l,3,5-triazine (RDX) in the air. The plasma emission spectra were recorded by an intensified charge-coupled device (ICCD) camera. The results showed that the plasma existed in the process of laser ablation of RDX. In the ultraviolet area, the main spectral lines were C I (187.46 nm and 223.01 nm), C II (323.1 nm) and N II (243.72 nm and 332.9 nm), while the dominating emission lines in the visible area were N II (393.9 nm and 454.7 nm), O II (490.75 nm) and O III (401.2 nm). Under experimental conditions, the intensities of the main peaks grew obviously with the increasing of the pulse delay, but laser energy didn’t have so much effect on the spectra. The ionization of the air almost did not influence plasma emission lines of RDX.