C Nanoparticles Laser Desorption Ionization to Produce Heavy Cations

Polycyclic Aromatic Hydrocarbons (PAHs) are important chemical species in combustion processes, energy, environment, health and industry. In this work, the recombination of the azulene, acenaphthene, anthracene, and pyrene PAHs ions with electrons is studied with the FlaPI (Flowing Afterglow with Photo Ions) method. The ionic species in the flowing afterglow are spatially characterized by a MS and the electron concentration is measured by means of a movable Langmuir probe. A new method L2DI (laser desorption / laser ionization) combined with the FlaPI methods developed for studying the recombination kinetics of much larger PAHs. The PAH ions concentration decay in time in function of the presence of electrons is measured. Different methods for recovering the recombination rate coefficient are assessed. A CRESU reactor is used to produce nanoparticles of PAH molecules at low temperature, which are deposited onto chosen surfaces. The samples were then analyzed ex-situ by AFM (Atomic Force Microscopy) in tapping mode. This method of characterization was tested previously by analyzing small soot particles generated by a diffusion flame and deposited onto mica surfaces.