Electron-capture detection, assignment

A wide variety of other MS techniques are used to detect explosives. Two notable techniques are Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and CE-MS. FT-ICR-MS is used to probe pseudomolecular ion formation of RDX, PETN, and TNT using several ionization sources including EDI, El, electron capture ionization (EC), and chemical ionization (Cl). Analyses are performed both in the positive and negative ionization mode, and identities are assigned to the major pseudomolecular ion peaks seen in the spectra from each explosive [198]. TTie composition of several explosive compounds from postblast residue is assessed with FT-ICR-MS by identifying the explosive and inactive ingredients in a smokeless powder, TNT,... 

Deep state experiments measure carrier capture or emission rates, processes that are not sensitive to the microscopic structure (such as chemical composition, symmetry, or spin) of the defect. Therefore, the various techniques for analysis of deep states can at best only show a correlation with a particular impurity when used in conjunction with doping experiments. A definitive, unambiguous assignment is impossible without the aid of other experiments, such as high-resolution absorption or luminescence spectroscopy, or electron paramagnetic resonance (EPR). Unfortunately, these techniques are usually inapplicable to most deep levels. However, when absorption or luminescence lines are detectable and sharp, the symmetry of a defect can be deduced from Zeeman or stress experiments (see, for example, Ozeki et al. 1979b). In certain cases the energy of a transition is sensitive to the isotopic mass of an impurity, and use of isotopically enriched dopants can yield a positive chemical identification of a level. 

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