Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)
O 35.90: Poster
Tuesday, March 27, 2012, 18:15–21:45, Poster B
Dynamic space charge effects in time-resolved photoelectron spectroscopy — •Lars Oloff, Stefan Hellmann, Christian Sohrt, Ankatrin Stange, Timm Rohwer, Michael Bauer, Lutz Kipp, and Kai Rossnagel — Institut für Experimentelle und Angewandte Physik, Universität Kiel, 24118 Kiel, Germany
The development of fs-pulsed lightsources, e.g. Free-Electron Lasers or High Harmonic Generation sources (HHG), opened up a new field of photoelectron spectroscopy (PES) in terms of time-resolved pump-probe-experiments. The high intensity of these sources leads to the effect that the interaction beween the photoelectrons emitted in such an ultrashort time frame can not be neglected anymore. This phenomenon known as space charge effect results in general in non-negligible impact on kinetic energy and detected angle of the emittted electrons. Specifically in time-resolved pump-probe-PES in the high pump-power regime a further intensity-caused effect can be recognized: Via multi-photon-processes the low energy pump-pulse may lead to unwanted emission of electrons from the material. This pump electron cloud interacts via Coulomb forces with the electron cloud emitted through the probe pulse resulting in shifted and broadened photoelectron spectra. We investigated these dynamic space charge effects at a HHG source (42.66 eV, 27th Harmonic) on TiSe2 and Pt(111) demonstrating their dependency on material, intensity and chosen delay between the two pulses. The results can be interpreted via molecular dynamic simulations.