Ion mobility spectrometer with ion source based on laser-irradiated porous silicon

A new ion source for ion mobility spectrometry based on UV laser action upon the surface of porous silicon, is described for the first time. It is found that the yield of TNT negative ions from this source is higher by an order of magnitude than in the case of multistep laser ionization of TNT-containing air mixture. It is established that factors important for the formation of negative ions in the case of continuous supply of analyt to the ionization region are (i) electron emission from the irradiated surface and (ii) subsequent ionmolecular reactions in the gas phase.