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2 October 2008 Detection of explosive related nitroaromatic compounds (ERNC) by laser-based ion mobility spectrometry
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In this study two issues are addressed, namely laser ionisation of selected nitroaromatic compounds (NAC) and the characterisation of their anions by photodetachment (PD) spectroscopy. Laser ionisation of the NAC at λ = 226.75 nm is investigated by ion mobility (IM) spectrometry at atmospheric pressure. The main product after laser ionisation is the reactive NO+ ion formed in a sequence of photofragmentation and multiphoton ionisation processes. NO+ is trapped by specific ion molecule reactions (IMR). Alternatively, NO, added as laser dopant, can directly be ionised. The formed NO+ reacts with the NAC under complex formation. This allows fragmentless NAC detection. The combination of IM spectrometry and PD spectroscopy provides real-time characterisation of the anions in the IM spectrum. This is useful to differentiate between NAC and interfering substances and, thus, to reduce false-positive detections of NAC. The electrons detached by the PD laser at λ = 532 nm are detected in the same spectrum as the anions. The potential of PD-IM spectrometry in terms of cross section determination, analytical improvements, tomographic mapping, spatial hole burning etc., is outlined.
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Robert Laudien, Daniel Riebe, Toralf Beitz, and Hans-Gerd Löhmannsröben "Detection of explosive related nitroaromatic compounds (ERNC) by laser-based ion mobility spectrometry", Proc. SPIE 7116, Optically Based Biological and Chemical Detection for Defence IV, 71160T (2 October 2008); doi: 10.1117/12.800455;

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