Ullrich Pietsch

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Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers (FEL), deliver ultra-brilliant ( 10–10 photons per bunch) coherent radiation in femtosecond ( 10– 100 fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection(More)
Surface relief gratings on azobenzene containing polymer films were prepared under irradiation by actinic light. Finite element modeling of the inscription process was carried out using linear viscoelastic analysis. It was assumed that under illumination the polymer film undergoes considerable plastification, which reduces its original Young's modulus by at(More)
An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in(More)
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 and imaginary parts of the refractive index n = 1 - delta + ibeta close to the boron K edge (approximately 188 eV). Prior to soft x-ray measurements, the structural parameters of the multilayers were determined by x-ray(More)
A phase transition in an amphiphilic mesophase is explored to deliberately induce mechanical strain in an assembly of tightly coupled metal ion coordination centers. Melting of the alkyl chains in the amphiphilic mesophase causes distortion of the coordination geometry around the central transition metal ion. As a result, the crystal field splitting of the(More)
Self-assembly of Fe(2+) or Ni(2+) ions and the ditopic ligand 6,6',6''-bis(2-pyridyl)-2,2':4',4'':2'',2'''-quaterpyridine (btpy) through coordinative binding results in rodlike metallosupramolecular coordination polyelectrolytes (Fe-MEPE or Ni-MEPE). Sequential self-assembly with dihexadecyl phosphate (DHP) via electrostatic interactions between MEPE and(More)
Using scanning X-ray diffraction microscopy with a spot size of 220 x 600 nm, it was possible to inspect individual GaAs nanorods grown seed-free through circular openings in a SiN(x) mask in a periodic array with 3 microm spacing on GaAs[111]B. The focused X-ray beam allows the determination of the strain state of individual rods and, in combination with(More)
Grazing incidence small-angle X-ray scattering (GISAXS) is used for nondestructive characterization of colloidal crystals of different numbers of hexagonally dense packed layers fabricated by convective self-assembly. Whereas small crystallites with random orientation were obtained in case of monolayers, the scattering data obtained from multilayer samples(More)
Self-assembly of Fe(2+) ions and the rigid ditopic ligand 1,4-bis(2,2':6',2''-terpyridin-4'-yl)benzene results in metallo-supramolecular coordination polyelectrolytes (MEPE). Sequential self-assembly of MEPE and dialkyl phosphoric acid esters of varying chain length via electrostatic interactions leads to the corresponding polyelectrolyte-amphiphile(More)
A detailed structural analysis of a Langmuir-Blodgett (LB) multilayer composed of a polyelectrolyte-amphiphile complex (PAC) is presented. The PAC is self-assembled from metal ions, ditopic bis-terpyridines, and amphiphiles. The vertical structure of the LB multilayer is investigated by X-ray reflectometry. The multilayer has a periodicity of 57 A, which(More)