Diagnosis of a benzene discharge with a mass-selective spectroscopic technique Original Research Article

The products formed in a benzene discharge have been probed by resonant two photon ionization spectroscopy. The molecules formed are cooled in a supersonic expansion and mass-analysis combined with spectroscopic information is used to identify the species. By this means styrene, phenylacetylene, methylstyrene, indene, fluorene and tolane are recognized. No six-ring polycyclic aromatic hydrocarbon could be detected. With this method the plasma is sampled at an early stage where the ethynylated and cyclopentafused polycyclic aromatic hydrocarbons are more abundant than the more stable six-ring ones. The coupling of a discharge source to a REMPI detection system enables electronic spectra of neutral molecules to be obtained which can be used to study their role in combustion processes, plasmas as well as in astrophysics.