Science and Technology of Energetic Materials

Vol.70, No.3 (2009)

Research paper

Detection of explosives using a vacuum ultraviolet ionization time-of-flight mass spectrometry (VUV-TOFMS)
Rumiko Hayashi, Wasana Kowhakul, Akio Susa, and Mitsuo Koshi


In recent years, real-time monitoring devices for explosives are highly needed to safeguard against terrorism. The vacuum ultra-violet single photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) is expected as one of the attractive options for rapid and sensitive detection of explosives. Especially for 2,3-dimethyl-2,3-dinitrobutane (DMNB) which is explosive taggant species, it is very important to know its mass spectrum pattern for the practical applications. To evaluate the possibility of explosives detection using the VUV-SPI-TOFMS at 10.5 eV, ionization energies of typical explosives and explosives-related compounds (ERCs) were estimated by density functional theory (DFT) calculations. From the calculation results, it is suggest that most of explosives and ERCs can be ionized with a 10.5 eV photon energy. Though calculated ionization energy of DMNB is 9.38 eV according to a DFT calculation, a clear parent peak is not observed in the mass spectrum of DMNB measured by the VUV-SPI-TOFMS at 10.5 eV. Instead, many peaks which include the thermal decomposition products are observed in the mass spectrum of DMNB. From the DFT calculations, it is shown that a peak at m/z=84 cation which is caused by the elimination of two NO2 groups can be produced by the ionization at 10.5 eV.

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VUV-SPI-TOFMS, Detection of explosives, DMNB, DFT calculations

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