A5042183960- Advanced X-ray Imaging Techniques
- Advanced Electron Microscopy Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Laser Material Processing Techniques
- Laser-Plasma Interactions and Diagnostics
- Ion-surface interactions and analysis
- Electron and X-Ray Spectroscopy Techniques
- Laser-induced spectroscopy and plasma
- Conducting polymers and applications
- Laser-Matter Interactions and Applications
- Organic Electronics and Photovoltaics
- Magnetic properties of thin films
- Crystallography and Radiation Phenomena
- Particle Accelerators and Free-Electron Lasers
- Advanced Materials Characterization Techniques
- Magneto-Optical Properties and Applications
- Photonic Crystals and Applications
- Magnetic Properties and Applications
- Diamond and Carbon-based Materials Research
- Photorefractive and Nonlinear Optics
- Lanthanide and Transition Metal Complexes
- Thin-Film Transistor Technologies
- Optical Systems and Laser Technology
- Luminescence Properties of Advanced Materials
- Spectroscopy and Quantum Chemical Studies
Folkwang University of the Arts
2014-2024
University of Siegen
2010-2024
Singulus (Germany)
2017
Elettra-Sincrotrone Trieste S.C.p.A.
2017
National Academy of Sciences of Belarus
2003
While chiral spin structures stabilized by Dzyaloshinskii-Moriya interaction (DMI) are candidates as novel information carriers, their dynamics on the fs-ps timescale is little known. Since with bulk Heisenberg exchange and interfacial DMI two distinct mechanisms at play, ultra-fast of order needs to be ascertained compared conventional collinear order. Using an XUV free-electron laser we determine temporal evolution in domain walls a magnetic thin film sample IR pump - X-ray scattering...
We utilize coherent femtosecond extreme ultraviolet (EUV) pulses derived from a free electron laser (FEL) to generate transient periodic magnetization patterns with periods as short 44 nm. Combining spatially excitation resonant probing at the dichroic M-edge of cobalt allows us create and probe gratings electronic magnetic excitations in CoGd alloy. In demagnetized sample, we observe an 50 fs rise time close FEL pulse duration ~0.5 ps decay within range for electron-phonon relaxation...
The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, chemistry biology, giving researchers access X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided pulses at a relatively low repetition rate, limited data statistics. Here, results the first megahertz-repetition-rate scattering experiments Spectroscopy Coherent Scattering (SCS) instrument European...
Observing ultrafast laser-induced structural changes in nanoscale systems is essential for understanding the dynamics of intense light-matter interactions. For laser intensities on order ${10}^{14}\phantom{\rule{4pt}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$, highly collisional plasmas are generated at and below surface. Subsequent transport processes such as heat conduction, electron-ion thermalization, surface ablation, resolidification occur picosecond nanosecond timescales. Imaging methods,...
Soft-x-ray Bragg reflection from two Ru/B(4)C multilayers with 10 and 63 periods was used for independent determination of both real imaginary parts the refractive index n = 1 - delta + ibeta close to boron K edge (approximately 188 eV). Prior soft x-ray measurements, structural parameters were determined by reflectometry using hard x rays. For 63-period sample, optical properties based on predictions made elemental major deviations found 10-period sample explained chemical bonding B(4)C...
Exciting a ferromagnetic material with an ultrashort IR laser pulse is known to induce spin dynamics by heating the system and ultrafast diffusion processes. Here, we report on measurements of spin-profiles properties in vicinity domain walls interface region between metallic Al layer Co/Pd thin film upon excitation. We followed temporal evolution means resonant magnetic scattering experiment surface geometry, which enables us exploit network within 1/e distance 3 nm 5 from Al/FM interface....
In this work, in situ studies of organic thin films under stretching are developed. A high efficiency PffBT4T-2OD π-conjugated polymer (PCE11) was coated directly on a stretchable substrate order to examine the impact tensile strain structural properties. For that purpose, grazing incidence x-ray diffraction coupled with optical microscopic observations have been carried out measure parameters PCE11 and probe mechanical behavior chains uniaxial load. It is observed range between 0% 15%–20%...
A scattering scheme to probe the time evolution of femtosecond pulses a soft X-ray free-electron laser (FEL) in multilayer structure is presented. The response periodic multilayers (MLs) with low and high absorption various numbers bi-layers pulse train Gaussian-shaped sub-pulses calculated. During passage incident interaction length increases profile changes as function spatial position within sample. Owing stretching reflected compared pulse, time-dependent ML can be visualized along...
Energy dependence of the optical constants boron carbide in short period Ru/B(4)C and Mo/B(4)C multilayers (MLs) are evaluated from complete reflectivity scans across K edge using energy-resolved photon-in-photon-out method. Differences between refractive indices B(4)Cmaterial inside close to surface obtained peak profile first order ML Bragg reflection near critical angle total external surface. Where a with narrow barrier layers appears as homogeneous at all energies, exhibits another...
We report the results of resonant magnetic XUV reflectivity experiments performed at free-electron laser FERMI. Circularly polarized light with photon energy tuned to Fe M2,3 edge is used measure reflectivities and corresponding Q-resolved asymmetry a Permalloy/Ta/Permalloy trilayer film. The exhibits ultrafast changes on 240 fs time scales upon pumping ultrashort IR pulses. Depending value wavevector transfer Qz, we observe both decreasing increasing values parameter, which attributed in...
The time evolution of the electron density and resulting dependence Fourier components X-ray polarizability a crystal irradiated by highly intense femtosecond pulses an free-electron laser (XFEL) is investigated theoretically on basis rate equations for bound electrons Boltzmann equation kinetics unbound gas. photoionization, Auger process, electron-impact ionization, electron-electron scattering three-body recombination have been implemented in system equations. An algorithm numerical...
Abstract Recent experiments on a soft X‐ray free‐electron laser (FEL) source (FLASH in Hamburg) have shown that multilayers (MLs) can be used as optical elements for highly intense irradiation. An effort to find most appropriate MLs has consider the femtosecond time structure and particular photon energy of FEL. In this paper we analysed response ‘low absorbing’ (e.g. such La/B 4 C) function number periods. Interaction pulse train Gaussian shaped sub‐pulses using realistic ML grown by...
The advent of free electron lasers has opened the opportunity to explore interactions between extreme ultraviolet (EUV) photons and collective excitations in solids. While EUV transient grating spectroscopy, a noncollinear four-wave mixing technique, already been applied probe coherent phonons, potential radiation for studying nanoscale spin waves not harnessed. Here we report experiments with magnons Fe/Gd ferrimagnetic multilayers. Magnons tens nanometers wavelengths are excited by pair...
Femtosecond high-intensity laser pulses at intensities surpassing $10^{14} \,\text{W}/\text{cm}^2$ can generate a diverse range of functional surface nanostructures. Achieving precise control over the production these structures necessitates thorough understanding morphology dynamics with nanometer-scale spatial resolution and picosecond-scale temporal resolution. In this study, we show that individual XFEL elucidate structural changes on surfaces induced by laser-generated plasmas,...
Femtosecond high-intensity laser pulses at intensities surpassing 1014 W/cm2 can generate a diverse range of functional surface nanostructures. Achieving precise control over the production these structures necessitates thorough understanding morphology dynamics with nanometer-scale spatial resolution and picosecond-scale temporal resolution. In this study, we show that single XFEL elucidate structural changes on surfaces induced by laser-generated plasmas using grazing-incidence small-angle...
The influence of annealing temperature on the structural and electrical properties conjugated poly(dodecyl-quaterthiophene) (PQT-12) polymer films is exploited. induced changes parameters are monitored by in situ grazing incident X-ray diffraction (GIXD) conductivity. They complemented studies dielectric using variable angle spectroscopic ellipsometry (VASE). An increase scattered intensity, size crystalline domains, current response observed for a first thermal cycle with stepwise heating...
Effect of the parametric beam instability (PBI) relativistic electron in a crystal was analyzed theoretically in<sup>1</sup> (see also<sup>2</sup>). This effect is analogous to self-amplification spontaneous emission (SASE) mechanism for X-ray Free Electron Laser (XFEL) with an undulator. However, case PBI transversal modulation defined by channeling and longitudinal arises because radiation mechanism. It shown present paper that current density J bunch typical FEL facility enough...
We describe the impact of tensile strains on structural properties thin films composed PffBT4T-2OD π-conjugated polymer and PC71BM fullerenes coated a stretchable substrate, based novel approach using in situ studies flexible organic films. In grazing incidence X-ray diffraction (GIXD) measurements were carried out to probe ordering polymers measure strain chains under uniaxial tests. A maximum 10% stretching was applied (i.e., beyond relaxation threshold). Interestingly we found different...
Gas-bubble superlattices produced in certain metals upon ion implantation of inert gases are treated for the first time regarded as weak 3D photonic crystals soft x-ray radiation. Computations based on electromagnetic transfer matrix method show that bcc helium bubbles molybdenum with lattice constant 5.0 nm and bubble diameters 2.4 3.0 will exhibit selective reflection x-rays wavelengths around to 10 nm. The reflectivity peaks have relative widths less than one per cent peak values range 2-...
We present a theoretical justification for method of extracting supplementary information the phase retrieval procedure taken from diffraction fs-pulses X-ray Free Electron Laser facilities. The approach is based on numerical simulation dynamics electron density in crystal composed different atoms unit cell, namely bi-atomic containing heavy and light atoms. It shown that evaluation intensities measured by means values XFEL pulse parameters enables to find absolute structure factors both...
The time evolution of the electron density and resulting dependence X-ray diffraction peak intensity in a crystal irradiated by highly intense femtosecond pulses an XFEL is investigated theoretically on basis rate equations for bound electrons Boltzmann equation kinetics unbound gas that plays essential role crystal. photoionization, Auger process, electron-impact ionization, electron--electron scattering, three-body recombination have been implemented system equations. An algorithm...
Interaction of the X-ray Free Electron Laser (XFEL) femtosecond pulses with a crystal is investigated beyond means conventional linear response theory. In order to analyze time dependence scattering properties we electron density evolution on basis rate equations.<sup>1</sup> take into account influence plasma that appears due ionization atoms couple system equations Boltzmann kinetic equation. As result, master involves such channels as: photoionization, Auger recombination, impact...