Diagnosis of a benzene discharge with a mass-selective spectroscopic technique

The products formed in a benzene discharge have been probed by resonant two photon ionization spectroscopy. The molecules formed are cooled in a super sonic expansion and mass-analysis combined with spectroscopic information i s used to identify the species. By this means styrene, phenylacetylene, met hylstyrene, indene, fluorene and tolane are recognized. No six-ring polycyc lic aromatic hydrocarbon could be detected. With this method the plasma is sampled at an early stage where the ethynylated and cyclopentafused polycyc lic aromatic hydrocarbons are more abundant than the more stable six-ring o nes. The coupling of a discharge source to a REMPI detection system enables electronic spectra of neutral molecules to be obtained which can be used t o study their role in combustion processes, plasmas as well as in astrophys ics. (C) 2001 Elsevier Science B.V. All rights reserved.