Charge and energy transfer processes at organic-metal interfaces are of key relevance in molecular electronics and functionalization of surfaces with molecular switches. Therefore the electronic structure and femtosecond electron dynamics of self-assembled monolayers (SAMs) of azobenzene-functionalized alkanethiols on gold have been investigated with time-resolved two-photon photoemission...
We investigate coherent phonon propagation in a thin film of ferroelectric Pb(Zr0.2Ti0.8)O3 (PZT) by ultrafast X-ray diffraction (UXRD) experiments, which are analyzed as time-resolved reciprocal space mapping (RSM) in order to observe the in- and out-of-plane structural dynamics simultaneously.[1] The mosaic structure of the PZT leads to a coupling of the excited out-of-plane expansion to...
In the last decade hard x-ray high kinetic energy photoelectron spectroscopy (HAXPES or HIKE) has led to a break-through in the field of photoemission due to its non destructive way of investigating the bulk electronic properties of materials and in particular buried interfaces in layered systems. Nanolayered systems are the keystones of current and future devices. The electronic, magnetic and...
Lattice vibrations after femtosecond laser excitation can be launched by different processes such as the relaxation of hot electrons or the coupling of the laser pulses to the lattice via nonlinear-optical mechanisms. The pathway and time scale of energy transfer form photonic excitation to the phononic subsystem is of fundamental interest to understand various physical phenomena like e.g....
State-selected aligned and oriented molecular ensembles serve as ideal samples to study ultrafast molecular dynamics in the molecular frame. Possible probing mechanisms are the investigation of molecular-frame photoelectron angular distributions or the detection of structural changes via X-ray and electron diffraction.
We have developed techniques to manipulate the motion of molecules in...
The current status of project P2 “Ultrafast charge transfer and isomerization dynamics of molecules” will be presented. The goal is to resolve the early-stage dynamics of energy relaxation concomitant with structural rearrangements in Fe(CO)5 in the gas phase. Photoexcitation generates a metal-to-ligand charge transfer in Fe(CO)5 that launches a sequence of processes on time scales of 20-30 fs...
Experimentally determined adsorption geometries of molecular switches are essential both for understanding their functionalities and for benchmarking ab initio calculations. The prototypical molecular switch azobenzene is investigated on the Ag(111) surface by means of the normal incidence x-ray standing wave (NIXSW) technique and dispersion-corrected density functional theory (DFT)...
Motivated by the x-ray induced ultra-fast transient drop of optical reflectivity of semi-conductors, we performed time-resolved photoemission (trPES) experiments with x-ray pump x-ray probe in order to understand the x-ray induced changes in the electronic structure of GaAs(100). To accomplish our measurements we were using the split-and-delay unit at PG2 beamline at the free-electron laser...
We present recent results from ultrafast laser-driven magnetization
dynamics experiments on the rare-earth local-moment ferromagnets
Gadolinium and Terbium. Our experiment combines angle-resolved photoemission
spectroscopy (ARPES) with the VUV photon energies and time resolution made possible by high-order harmonic generation to scrutinize the non-equilibrium band structure...
Time resolved photoemission from core levels (trPES) at FELs is a tool for studying surface dynamics in real-time. Basis for this is the sensitivity of core-levels to their chemical environment. By probing their spectral evolution after an ultra-short excitation one can get insight on both, electronically caused excitations (fs- up to several-ps time-scales) as well as responses of the crystal...
