NEW ASPECTS OF GROWTH MECHANISMS FOR POLYCYCLIC AROMATIC-HYDROCARBONSIN-DIFFUSION FLAMES

Two-photon ionization time-of-flight mass spectroscopy is used to anal yze combustion products from laminar methane diffusion flames. High-re solution height profiles in the symmetry axis of the flame show sensit ively the rise and decay of concentrations of various polycyclic aroma tic hydrocarbons (PAH) in the mass range up to 472 amu. From a compari son of these profiles in dependence of the carbon content of the PAH, we derive fingerprints both of successive acetylene addition and of re active coagulation as growth mechanisms of PAH.