Three aliphatic nitroalkanes, nitromethane, nitroethane, and 1-nitropropane, are investigated with fs laser-induced filament and breakdown spectroscopy (LIFBS). Filament emission spectra, C I, the CN violet system (BΣ - XΣ, Δ = 0 sequence), and the C swan system (dΠ - aΠ, Δ = 0 sequence), are obtained. The time integrated intensities of CN and C can be used for identifying the three nitroalkanes. The filament features (length, diameter, and temperature) of the CN and C emissions are analyzed; C converts to CN through a single-atom substitution reaction between C and N atoms at the early stage, which mainly occurs at the head and tail parts of the filament with a lower temperature rather than at the hotter middle part.
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