Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 28: Photochemistry

MO 28.2: Talk

Friday, March 22, 2013, 11:30–11:45, F 102

The Photodissociation Dynamics of the Ethyl Radical, C2H5, Investigated by Velocity Map Imaging — •Jens Giegerich, Kathrin H. Fischer, Michael Steinbauer, and Ingo Fischer — University of Würzburg, Institute for Physical and Theoretical Chemistry, Am Hubland Süd, 97074 Würzburg, Germany

Ethyl radicals were generated from n-propyl nitrite as a precursor, which decomposes to the desired radical in a vacuum jet flash pyrolysis source. The radicals were excited to the à 2A* (3s) Rydberg state around 250 nm. At this wavelength region the energetically most favorable reaction channel is the dissociation to C2H4 (ethane) + H. The H-atom dissociation products were ionized in a [1+1*] REMPI process via the 1s-2p transition and recorded on a Velocity Map Imaging Detector. The observed translational energy distribution is bimodal. A contribution of slow H-atoms with an isotropic angular distribution, typical for statistical dissociation reactions, peaks at low translational energies. A fast H-atom channel with an anisotropic angular distribution, typical for a direct dissociation process, peaks at around 1.8 eV. Time-delay scans with varying extraction voltages were carried out in addition to the Velocity Map Imaging experiments. These scans indicate the presence of two rates for the formation of H-atoms. One rate with a sub-nanosecond time constant is connected with H-atoms with large translational energy. The second rate with a time constant on the order of 100 ns is connected with H-atoms formed with low translational energy.