Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 1: Photochemistry

MO 1.4: Talk

Monday, March 6, 2017, 15:30–15:45, N 6

The Photodissociation of the ortho- & para-Xylyl Radical, C8H9, Investigated by Velocity Map Imaging — •Kai Pachner and Ingo Fischer — Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Deutschland

Xylyl radicals can be found as intermediates in combustion processes. Their parent molecules, the xylenes, are used as additives in fuels to increase antiknock properties. The thermal decomposition of the xylyl radicals has been explored recently by Hemberger et al. in a synchrotron experiment [1]. Based on these studies, we investigated the photodissociation of the ortho- & para-xylyl radical using velocity map imaging. Xylyl radicals were formed via flash pyrolysis in a pulsed molecular beam using 2-/4-methylphenethyl nitrite as a precursor. Irradiation of the xylyl radical with UV light around 310nm leads to the formation of the corresponding xylylenes for both radicals, or benzocyclobutene for the ortho-xylyl radical respectively, by hydrogen atom loss. Generated hydrogen fragments are then ionized in a [1+1']-REMPI process via the 1s-2p transition and detected on a velocity map imaging detector. The translational energy distribution of the hydrogen fragments as well as their angular distribution and rate constants for the hydrogen atom loss indicate a statistical dissociation in the ground state or an indirect dissociation in the excited state.

[1] Hemberger et al., J. Phys. Chem. A, 2014, 118, 3593 - 3604.