LASER IONIZATION STUDIES OF NITROAROMATIC AND NOX(X = 1 OR 2) MOLECULES IN THE REGION 224-238 NM (VOL 124, PG R 15, 1993)

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) mo lecules from which it may have originated and to provide information a bout possible energy pathways in the fragmentation processes. The part icular studies described in this paper were carried out to identify wa velength regions where greater ionisation efficiency of the NO molecul e arising from the nitroaromatic molecules could be achieved. In the c ourse of these studies an important difference in the NO+ wavelength d ependent ionisation spectra of nitrobenzene and o-nitrotoluene was obs erved. The observation of atomic oxygen resonances in the nitrobenzene and NO2 spectra suggest that similar pathways are being followed in t hese two dissociating molecules.