RESONANT IONIZATION SPECTROSCOPY OF CARBON-ATOMS FOLLOWING LASER-INDUCED FRAGMENTATION OF NITROAROMATIC MOLECULES

During the course of studies on resonance enhanced multiphoton ionization (REMPI) spectra of nitro-aromatic molecules, a number of sharp atomic transitions were observed among the broad molecular peaks of the C-12(+) spectrum in the wavelength region 245-260 nm. These have been unambiguously identified as transitions in atomic carbon from both ground and excited states. In addition, laser fluence measurements on two of these transitions exhibit a sixth order power dependence on resonance and a cubic dependence off resonance. This can be explained by a model requiring three photons to produce a neutral carbon atom from the parent molecule together with a further three photons to ionize.