Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 94: Ultrafast Surface Dynamics II

O 94.6: Talk

Friday, March 11, 2016, 12:00–12:15, S054

Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy — •Lars-Philip Oloff, Kerstin Hanff, Ankatrin Stange, Gerald Rohde, Florian Diekmann, Michael Bauer, and Kai Rossnagel — Insitut für Experimentelle und Angewandte Physik, Universität Kiel, 24098 Kiel, Germany

The development of fs-pulsed XUV sources such as free-electron lasers or high-harmonic-generation (HHG) sources has opened up a new scientific field for photoelectron spectroscopy in terms of time-resolved pump-probe experiments. While the impact of the high peak brilliance of these novel sources on photoemission spectra has been studied extensively, the effect of high pump fluences has not been investigated systematically yet. In the strong excitation regime, the low photon energy pump pulses may lead to the emission of electrons from the sample via multiple photon absorption, thus directly influencing the electrons ejected by the probe pulse through Coulomb interaction. We have systematically investigated these so called space-charge effects at a HHG source (22.3 eV) for the case of a graphite (HOPG) sample. Specifically, we have studied the influence on the photoelectron energy and momentum distributions as a function of power density, spot size, pump-probe delay, and pump wavelength. The results are interpreted in terms of a simple mean-field model.