@article{SaphiannikovaHennebergGeneetal.2004, author = {Saphiannikova, Marina and Henneberg, Oliver and Gene, T. M. and Pietsch, Ullrich and Rochon, Paul}, title = {Nonlinear effects during inscription of azobenzene surface relief gratings}, issn = {1520-6106}, year = {2004}, abstract = {Surface relief gratings were inscribed on azobenzene polymer films using a pulselike exposure of an Ar+ laser. The inscription process was initiated by a sequence of short pulses followed by much longer relaxation pauses. The development of the surface relief grating was probed by a He-Ne laser measuring the scattering intensity of the first- order grating peak. The growth time of the surface relief grating was found to be larger than the length of the pulses used. This unusual behavior can be considered as a nonlinear material response associated with the trans-cis isomerization of azobenzene moieties. In this study the polymer stress was assumed to be proportional to the number of cis-isomers. One-dimensional viscoelastic analysis was used to derive the polymer deformation. The rate of trans-cis isomerization increases with the intensity of the inscribing light; in the dark it is equal to the rate of thermal cis- trans isomerization. The respective relaxation times were estimated by fitting theoretical deformation curves to experimental data}, language = {en} } @article{SendAbboudHartmannetal.2013, author = {Send, Sebastian and Abboud, Ali and Hartmann, Robert and Huth, M. and Leitenberger, Wolfram and Pashniak, N. and Schmidt, J. and Str{\"u}der, Lothar and Pietsch, Ullrich}, title = {Characterization of a pnCCD for applications with synchrotron radiation}, series = {Nuclear instruments \& methods in physics research : a journal on accelerators, instrumentation and techniques applied to research in nuclear and atomic physics, materials science and related fields in physics ; A, Accelerators, spectrometers, detectors and associated equipment}, volume = {711}, journal = {Nuclear instruments \& methods in physics research : a journal on accelerators, instrumentation and techniques applied to research in nuclear and atomic physics, materials science and related fields in physics ; A, Accelerators, spectrometers, detectors and associated equipment}, number = {5}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0168-9002}, doi = {10.1016/j.nima.2013.01.044}, pages = {132 -- 142}, year = {2013}, abstract = {In this work we study the response of a pnCCD by means of X-ray spectroscopy in the energy range between 6 key and 20 key and by Laue diffraction techniques. The analyses include measurements of characteristic detector parameters like energy resolution, count rate capability and effects of different gain settings. The limit of a single photon counting operation in white beam X-ray diffraction experiments is discussed with regard to the occurrence of pile-up events, for which the energy information about individual photons is lost. In case of monochromatic illumination the pnCCD can be used as a fast conventional CCD with a charge handling capacity (CHC) of about 300,000 electrons per pixel. If the CHC is exceeded, any surplus charge will spill to neighboring pixels perpendicular to the transfer direction due to electrostatic repulsion. The possibilities of increasing the number of storable electrons are investigated for different voltage settings by exposing a single pixel with X-rays generated by a microfocus X-ray source. The pixel binning mode is tested as an alternative approach that enables a pnCCD operation with significantly shorter readout times.}, language = {en} } @article{SendAbboudLeitenbergeretal.2012, author = {Send, Sebastian and Abboud, Ali and Leitenberger, Wolfram and Weiss, Manfred S. and Hartmann, Robert and Str{\"u}der, Lothar and Pietsch, Ullrich}, title = {Analysis of polycrystallinity in hen egg-white lysozyme using a pnCCD}, series = {Journal of applied crystallography}, volume = {45}, journal = {Journal of applied crystallography}, number = {6}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0021-8898}, doi = {10.1107/S0021889812015038}, pages = {517 -- 522}, year = {2012}, abstract = {A crystal of hen egg-white lysozyme was analyzed by means of energy-dispersive X-ray Laue diffraction with white synchrotron radiation at 2.7 angstrom resolution using a pnCCD detector. From Laue spots measured in a single exposure of the arbitrarily oriented crystal, the lattice constants of the tetragonal unit cell could be extracted with an accuracy of about 2.5\%. Scanning across the sample surface, Laue images with split reflections were recorded at various positions. The corresponding diffraction patterns were generated by two crystalline domains with a tilt of about 1 degrees relative to each other. The obtained results demonstrate the potential of the pnCCD for fast X-ray screening of crystals of macromolecules or proteins prior to conventional X-ray structure analysis. The described experiment can be automatized to quantitatively characterize imperfect single crystals or polycrystals.}, language = {en} } @article{SendvonKozierowskiPanzneretal.2009, author = {Send, Sebastian and von Kozierowski, Marc and Panzner, Tobias and Gorfman, Semen and Nurdan, Kivanc and Walenta, Albert H. and Pietsch, Ullrich and Leitenberger, Wolfram and Hartmann, Robert and Str{\"u}der, Lothar}, title = {Energy-dispersive Laue diffraction by means of a frame-store pnCCD}, issn = {0021-8898}, doi = {10.1107/S0021889809039867}, year = {2009}, language = {en} } @article{SiebrechtSchreyerEnglischetal.1997, author = {Siebrecht, R. and Schreyer, A. and Englisch, Uwe and Pietsch, Ullrich and Zabel, Hartmut}, title = {The new reflectometer ADAM at the ILL}, year = {1997}, language = {en} } @article{StahnGeueGrenzeretal.2000, author = {Stahn, Jochen and Geue, Thomas and Grenzer, J{\"o}rg and Pietsch, Ullrich}, title = {Interaction of short-chain alkanes with surface and interfaces of multilayer films built from amphiphilic molecules: an in-situ X-ray and neutron scattering probe}, year = {2000}, language = {en} } @article{StahnMoehlePietsch1996, author = {Stahn, Jochen and M{\"o}hle, Marcus and Pietsch, Ullrich}, title = {Accurate structure determination for GaAs using Pendell{\"o}sung oscillation}, year = {1996}, language = {en} } @article{StahnMoehlePietsch1998, author = {Stahn, Jochen and M{\"o}hle, Marcus and Pietsch, Ullrich}, title = {Comparison of theoretical and experimental structure amplitudes of GaAs}, year = {1998}, language = {en} } @article{StahnPietschBlahaetal.2001, author = {Stahn, Jochen and Pietsch, Ullrich and Blaha, Pawel and Schwarz, K. H.}, title = {Electric field induced charge-density variations in covalently bonded compounds}, year = {2001}, language = {en} } @article{StahnPucherGeueetal.1998, author = {Stahn, Jochen and Pucher, Andreas and Geue, Thomas and Daniel, A. and Pietsch, Ullrich}, title = {Electric field induced electron density response of GaAs and ZnSe}, year = {1998}, language = {en} }