Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 2: Electronic Spectroscopy I

MO 2.1: Talk

Monday, March 18, 2013, 11:00–11:15, F 107

Phenylpropargyl Radicals and Their Dimerization Products: An IR/UV Double Resonance Study — •Jörg Herterich and Kathrin H. Fischer — Institut für Physikalische und Theoretische Chemie, Universität Würzburg

Two C9H7 isomers, 1-phenylpropargyl and 3-phenylpropargyl have been studied by IR/UV double resonance spectroscopy in a free jet. The species are possible intermediates in the formation of soot and polycyclic aromatic hydrocarbons (PAH). The radicals are generated by flash pyrolysis from the corresponding bromides and ionized at 255-297 nm in a one-color two-photon process. Mid-Infrared radiation between 500 and 1800 cm-1 is provided by a free electron laser (FEL). It is shown that the two radicals can be distinguished by their infrared spectra. In addition we studied the dimerization products originating from the phenylpropargyl self-reaction. We utilize the fact that the pyrolysis tube can be considered to be a flow reactor, permitting to investigate the chemistry in such a thermal reactor. Dimerization of phenylpropargyl produces predominately species with m/z=228 and 230. A surprisingly high selectivity has been found: The species with m/z=230 is identified to be para-terphenyl, while m/z=228 can be assigned to 1-phenylethynyl-naphthalene. The results allow to derive a mechanism for the dimerization of phenylpropargyl and suggest hitherto unexplored pathways to the formation of soot and PAH.