Alexander Föhlisch, PhD
|University of Hamburg
Faculty of Mathematics, Informatics and Natural Sciences
Department of Physics
Luruper Chaussee 149
At the core of my research stands the investigation of the electronic structure
and the ultrafast processes at surfaces, in molecules and solids in an atom specific
way. To this end soft X-ray spectroscopic methods with synchrotron radiation sources
and Free-Electron-Lasers (FEL) are used and developed further. Integral to my work
are close collaborations with theoretical groups.
The ultra fast charge transfer dynamic of atoms adsorbed on surfaces depends in fine
detail on the orbital overlap and the substrate electronic structure. With
core-hole-clock spectroscopy the charge transfer time of Sulfur on Ruthenium was
determined to 320 attoseconds. Resonance stabilization on adsorbates due to the
surface projected substrate band gap was determined experimentally and
theoretically. The method is currently extended to investigate spin polarized
To obtain an atom specific, chemical state selective and symmetry resolved
description of the adsorbate valence electronic structure is investigated with
resonant inelastic X-ray scattering, near edge X-ray absorption fine structure
and high resolution photoelectron spectroscopy and. In combination with ab initio
theory a significantly improved model of surface chemical bonding was achieved.
Fundamental aspects of X-ray spectroscopic methods.
The interpretation of resonant inelastic X-ray scattering as an atom specific and
orbital symmetry selective electronic structure tool for adsorbates was given.
Recently, the influence of ultra fast dynamics, vibronic coupling and Jahn–Teller
distortions have been elucidated in collaboration with theory. Also an upper
limit to interatomic coulomb decay in solids leading to a re-evalution of ‘multi
atom resonant photoemission’. Electron correlation was investigated by resonant
photoemission on transition metals Cu and Ni.
In the project “Multi-Photon and Non-Linear Processes as a Probe of Surfaces
Dynamics” (Föhlisch,Wurth 3-year proposal) the goal is to develop novel X-ray
spectroscopic tools, using the high brilliance and the short X-ray pulses of
the Hamburg FEL in order to investigate dynamic processes in an element
specific way. Also synchronized optical fs Lasers can be used. Here, concepts
for novel experiments are being developed. For X-ray pump/probe experiments
I develop a X-ray delay line based on a Mach-Zehnder interferometer with
reflection/transmission gratings as beam splitter and mixer. We envisage to
study electron correlation and dynamics and to establish novel spectroscopies
like time resolved anti-Stokes X-ray Raman scattering.
Amongst the first experiments at the Hamburg VUV FEL we conducted in 2005
fundamental experiments on the photoionization cross section of noble gases,
molecules and solids in high VUV radiation fields. In collaboration with M.
Wolf we conducted a run on doubly resonant Sum Frequency Generation with
Visible and VUV radiation to study magnetization dynamics and yield extreme
interface sensitivity with elemental contrast.