Stuttgart 2012 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 2: Electronic Spectroscopy
MO 2.3: Vortrag
Montag, 12. März 2012, 11:00–11:15, V38.02
Photoionisation of fluorenyl and diphenylmethyl — •Melanie Lang, Ingo Fischer, Patrick Hemberger, and Michael Steinbauer — Institute of Physical and Theoretical Chemistry of Würzburg, Am Hubland, D-97074 Würzburg, Germany
Due to environmental and health issues it is useful to reduce or prevent the formation of soot and polycyclic aromatic hydrocarbons (PAH). Therefore understanding soot and PAH formation is essential. We examined two radicals, fluorenyl (C13H9Br) and diphenylmethyl (C13H11) which are possible intermediates in hydrocarbon combustion. We used Synchrotron radiation as a tunable light source to carry out Threshold Photoelectron Photoion Coincidence (TPEPICO) Spectroscopy to determine ionization energies (IE) of both radicals. We used 9-bromofluorene (C13H9Br) as a precursor to create the fluorenyl and benzhydrylamine (C13H11NH2) as precursor for diphenylmethyl radical by flash pyrolysis. As both are solids at room temperature both precursors had to be heated to be transferred in the gas phase. The resulting threshold photoelectron spectra (TPES) of both radicals are presented. The extracted IE values are compared to previous results of other groups gained by electron impact experiments. For fluorenyl the comparison shows good agreement with the other results. In contrast the IE of diphenylmethyl detected by the TPES differs from the IE obtained by electron impact techniques. Reasons for this observation will be discussed. Since the precursor dissociative photoionization becomes important at moderate excess energies, it might be discussed whether experiments with different precursors should be carried out in addition.