LASER IONIZATION STUDIES OF NITROAROMATIC AND NOX(X = 1 OR 2) MOLECULES IN THE REGION 224-NM-238-NM

Wavelength dependent ionisation studies have been carried out on the n itroaromatic molecules nitrobenzene and o-nitrotoluene as well as NO a nd NO2 gases in the wavelength region 224-238 nm. Mass spectra from th e nitroaromatic molecules show extensive fragmentation with a particul arly prominent NO+ ion peak. This particular fragment ion has been of great importance, not only as a marker to identify the presence of a n itro-type compound, but also to distinguish from NO(x)(x = 1 or 2) mol ecules from which it may have originated and to provide information ab out possible energy pathways in the fragmentation processes. The parti cular studies described in this paper were carried out to identify wav elength regions where greater ionisation efficiency of the NO molecule arising from the nitroaromatic molecules could be achieved. In the co urse of these studies an important difference in the NO+ wavelength de pendent ionisation spectra of nitrobenzene and o-nitrotoluene was obse rved. The observation of atomic oxygen resonances in the nitrobenzene and NO2 Spectra suggest that similar pathways are being followed in th ese two dissociating molecules.