Moving spins in a labyrinth of magnetic domains
Published as: “Ultrafast optical demagnetization manipulates nanoscale spin structure in domain walls”, Nature Communications 3, 1100 (2012).When a magnetized material is bombarded by a femtosecond infra-red laser pulse, the magnetization of the material drops within a few hundreds of femtoseconds. In a study using ultrashort X-ray pulses delivered by FLASH we investigate the process of ultrafast demagnetization in a sample exhibiting nanometer-sized magnetic domains. In the pump-probe experiment the evolution of the magnetization is ...
Cut and paste zeolites
Published as: “Design of zeolite by inverse sigma transformation”, Nat. Mater. DOI: 10.1038/NMAT3455Zeolites are highly crystalline microporous materials. Their unique properties let them stand out in many applications such as adsorption, catalysis and separation. Inserting heteroelements often improves their desired properties. Germanium is known to direct towards extra-large pore zeolites but decreases stability. We managed to fully remove germanium from a germanosilicate zeolite by acid leaching while preserving the silicate ...
Superhelical architecture of myomesin
Published as: “Superhelical Architecture of the Myosin Filament-Linking Protein Myomesin with Unusual Elastic Properties”. PLoS Biol 10(2): e1001261. doi:10.1371/journal.pbio.1001261The process by which active muscles can generate substantial mechanical forces and still remain elastic and keep their overall organisation presents an interesting problem and one that is still not fully understood. Using a hybrid structural approach we have been able to determine the architecture of a section of the muscle filament linking protein ...
Putting the squeeze on nanocrystalline MgO: Nanomaterials are “softer” then their bulk counterparts
During the last decades, both extensive experimental and theoretical research has documented that the physical and chemical properties of polycrystalline solids are sensitive to the average crystallite size once it drops below a certain size, usually in the range of ~10-100 nm. This remarkable observation is related to both the different properties of the nano-crystals and the relatively large fraction of intercrystalline material. These observations open novel and unique ways to tune the physical and chemical properties of iso-chemical compounds by changing the average ...
Delocalized excitons in amorphous solids
Published as: “Evidence of delocalized excitons in amorphous solids”, Physical Review Letters 105, 116401 (2010).We studied the temperature dependence of the absorption coefficient of amorphous SiO2 near and above the fundamental band gap, as obtained by Kramers-Kronig dispersion analysis of reflectivity spectra. We demonstrate the main excitonic resonance at 10.4 eV to feature a close Lorentzian shape redshifting with increasing temperature. This provides a strong evidence of excitons being almost fully delocalized ...
Shooting an ultrafast electronic movie
Published as: “Ultrafast Melting of a Charge-Density Wave in the Mott Insulator 1T-TaS2”, Physical Review Letters 105, 187401 (2010).The combination of an optical laser with FEL pulses from FLASH in a pump-probe setup uniquely enables timeresolved core-level photoemission spectroscopy with high temporal and energy resolution. In a proof-ofprinciple experiment, a charge-density wave in the layered strongly correlated electron material 1T-TaS2 is driven out of equilibrium by an intense optical laser pulse and the subsequent ...
X-ray superradiance and the collective Lamb shift
Published as: “Collective Lamb Shift in Single-Photon Superradiance”, Science 328, 1248 (2010).An atom, after being resonantly excited by a pulse of radiation, will typically de-excite with a characteristic decay time. An ensemble of many identical atoms with just one of the atoms being excited will decay much faster than a single atom. This is a cooperative effect in the interaction of light and matter known as superradiance. We have prepared a superradiant system by embedding an ultrathin layer of resonant 57Fe nuclei in ...
Aquatic - paraffin coated - pentacene transistors for biosensing
Published as: “Pentacene Thin-Film Transistors Encapsulated by a Thin Alkane Layer Operated in an Aqueous Ionic Environment”, Advanced Materials 22, 4350–4354 (2010). Letters 105, 116401 (2010).Stable operation of pentacene thin-film transistors in an aqueous ionic environment was made possible by encapsulating them with a 50 nm thick layer of tetratetracontane (TTC, C44H90), a long chain alkane molecule. The morphology of the TTC film deposited on a pentacene thin film surface by thermal vacuum deposition ...
Delaying sample destruction in FLASH experiments
Published as: "Sacrificial Tamper Slows Down Sample Explosion in FLASH Diffraction Experiments", Physical Review Letters 104, 064801 (2010).Coating samples in a sacrificial external layer slows down the rate at which samples are damaged by the ultra-intense X-ray beam provided by the FLASH free electron laser. The extremely intense light produced by FLASH enables coherent imaging using single ultrafast X-ray pulses. The same intense pulse destroys the sample, and diffraction must occur before the X-ray beam significantly alters ...
Structural insights into the regulation of protein kinases
Published as: “Molecular basis of the death-associated protein kinase-calcium/calmodulin regulator complex”. Sci. Signal. 3, ra6 (2010).Investigating how cells communicate is fundamental to our understanding of biology. We have determined the first molecular structure of a protein kinase in complex with the universal regulator protein calmodulin and calcium. The structure, which provides a model for many other protein kinases, allows insight into how its function could be specifically blocked. Since the selected protein kinase is ...
Putting the squeeze on cuprate superconductors
Published as: “Spontaneous Symmetry Breaking by Charge Stripes in the High Pressure Phase of Superconducting La1.875Ba0.125CuO4”, Phys. Rev. Lett. 104, 057004 (2010).Competing magnetic and electronic interactions in the cuprate high temperature superconductors often result in nanoscale inhomogeneity of the charge and spin density, a property that could be relevant to the unconventional superconductivity. A very interesting example is the spin and charge stripe order in the copper-oxide planes of ...
Femtosecond snapshots of magnetic domains
Published as: “Single-pulse resonant magnetic scattering using a soft x-ray free-electron laser”, Phys. Rev. B 81, 100401 (R) (2010).Single-pulse resonant magnetic scattering experiments were performed by using soft X-ray pulses generated by the free-electron laser FLASH. A magnetic diffraction pattern was recorded from a Co/Pt multilayer sample at the Co M2,3 edge with a single 30 femtosecond long FEL pulse, without destroying the sample.
Imaging defects with coherent X-rays
Published as: “Coherent x-ray imaging of defects in colloidal crystals’’, Phys. Rev. B Vol. 81, 224105 (2010).Real crystalline materials, in contrast to the idealized model of a perfect crystal, contain a broad spectrum of defects. These defects determine most of the mechanical, optical and electronic properties of the crystals. Visualization of the defect core in a bulk material with X-ray methods still remains a challenge. Here we demonstrate how to use coherent X-ray diffractive imaging (CXDI) to map such defects in colloidal ...
Periodic dislocations in thin PbSe films
Published as: “Analysis of periodic dislocation networks using x-ray diffraction and extended finite element modeling”, Appl. Phys. Lett. 96, 131905 (2010).Self organization provides a possibility to create dislocation free regions in heteroepitaxial semiconductor structures in order to improve the quality of subsequently grown devices. In this work the statistical properties of a periodic array of dislocations in thin PbSe films deposited on a PbTe buffer were investigated by means of X-ray diffraction. A novel method for the ...
Rhodium advances the carbon age in nanoelectronics
Published as: “Study of the Interface between Rhodium and Carbon Nanotubes” ACS Nano 4, 1680 – 1686 (2010).Carbon nanoelectronics require the development of reproducible, high-quality ohmic contacts between carbon nanomaterials and their contact electrodes. The hunt is on for new candidate metals. We have followed the interface formation between rhodium and carbon nanotubes using X-ray photoelectron spectroscopy at 3.5 keV photon energy in combination with high-resolution transmission electron microscopy. Rh nucleates at defect ...
New algorithms for single-particle diffractive imaging
Published as: “Cryptotomography: Reconstructing 3D Fourier Intensities from Randomly Oriented Single-Shot Diffraction Patterns”, Phys. Rev. Lett. 104, 239902 (2010).A new method called cryptotomography combines two dimensional (2D) diffraction patterns of identical particles, each collected in a random and unknown orientation, to unravel the full three-dimensional (3D) image of the average particle. We carried out the first demonstration of cryptotomography by collecting diffraction patterns of ellipsoidal iron oxide nanoparticles at ...
Formation of 2D crystals on water via linearly polarized laser illumination
Published as: “Laser-Induced Alignment of Self-Assembled Films of an Oligopeptide β-Sheet on the Water Surface”, Angew. Chem. Int. Ed. 122, 2404–2407 (2010).A pulsed infrared laser beam was used to align oligopeptide molecules at the air-water interface. The oligopeptide was designed to form a cyclic β-strand dimer in a volatile solution. After spreading the solution onto the water surface, illumination with linearly polarized laser light during solvent evaporation induced formation of an aligned crystalline film, whereas ...
SAXS combined with crystallography examines molecular switch action
Published as: “Quaternary structure of the human Cdt1-Geminin complex regulates DNA replication licensing”, Proc. Natl. Acad. Sci. USA 106, 19807 (2009).Small angle scattering becomes a streamline tool in modern structural molecular biology providing valuable information about overall structure and conformational changes of native individual proteins and functional complexes. The variety of questions addressed by the technique ranges from evaluation of the overall geometrical parameters and low-resolution shape reconstruction to ...
Silicon melts in two steps
Published as: “The liquid-liquid phase transition in silicon revealed by snapshots of valence electrons”, Proc. Natl. Acad. Sci. USA 107, 39, 16772–16776 (2010).Microscopic models for the „anomalies of water“ are still lacking an experimental proof, although anomalous thermodynamic behaviour is common for a class of matter that forms tetrahedral networks - like water, diamond or silicon. Their phase diagrams are very rich, but the exploration of large areas has been limited mostly to theoretical studies. And yet, remainders of ...
Unexpected decoherence in attosecond photoionization
Published as: "Decoherence in attosecond photoionization", Phys. Rev. Lett. 106, 053003 (2011)Attosecond science holds the promise of controlling electron motion to manipulate physical processes at the atomic level. One way of inducing electron motion is photoionization using an attosecond laser pulse. The typical time scale of electronic motion in atoms, molecules, and condensed matter systems ranges from a few attoseconds (1as = 10 -18s) to tens of femtoseconds (1fs = 10 -15s) [1]. Remarkable progress in ...
Structural characterization of a complex that mediates termination of protein synthesis
Published as: “Structural insights into eRF3 and stop codon recognition by eRF1”, Genes and Development Vol. 23 No. 9, 1106-1118, (2009).Developments in Small-Angle X-ray Scattering (SAXS) at the EMBL, Hamburg Outstation made this method a high-throughput, low resolution tool providing information about overall structure and conformational changes of biological macromolecules in solution. SAXS is often employed along with protein crystallography to elucidate structure of functional complexes, such as that of proteins eRF1 and eRF3, ...
Magnetic stability at the nanoscale
Published as: “Stabilization of Antiferromagnetic Order in FeO Nanolayers”, Physical Review Letters 103, 097201 (2009).Ferromagnetic order in thin films is strongly affected when their thickness is reduced to the nanometre regime. The main reason for this are thermal excitations that lead to fluctuations of the magnetic moments. It is well known that thick antiferromagnetic buffer layers with a high magnetic anisotropy can be used to stabilize magnetic order in ultra-thin ferromagnetic films. This effect is of high importance for ...
Order in disorder uncovered by X-ray speckle cross correlation
Published as: “X-ray cross correlation analysis uncovers hidden symmetries in disordered matter”, Proceedings of the National Academy of Sciences 106, 11511-11514 (2009).The different local symmetries in colloidal glasses were investigated by coherent X-ray scattering beyond the standard pair correlation analysis. By analyzing the resulting speckle patterns with a newly developed X-ray cross correlation analysis (XCCA) concept, it is possible to access and classify the otherwise hidden local order within disorder. Four-, six-, ten- ...
High resolution structures of protein complexes to understand the molecular architecture of human muscle cells
Published as: "Terminal assembly of sarcomeric filaments by intermolecular beta-sheet formation". Trends Biochem Sci. 34, 33-39 (2009). PubMed PMID: 18996015.The contraction/relaxation cycle of muscle cells translates into large molecular movements of several filament systems in sarcomeres, requiring special molecular mechanisms to maintain their structural integrity. Recent structural and functional data from filaments with extensive arrays of immunoglobulin-like domains have for the first time unravelled a common function of their ...
Origin and temperature dependence of radiation damage in biological samples at cryogenic temperatures (in-house research performed at the PSI)
Published as: “Origin and temperature dependence of radiation damage in biological samples at cryogenic temperatures”, PNAS, vol. 107, no. 3, 1094-1099 (2010).Radiation damage to biological samples has become a major limitation for experiments at brilliant 3rd generation synchrotron sources such as Petra III and free electron lasers. Radiation damage leads to sample deterioration and hence drastically limits the applicability of experimental techniques employing high doses of radiation [1, 2]. Cryo-cooling of samples down to 100 K or ...
X-ray absorption spectroscopy at FLASH
Published as: “Near edge X-ray absorption fine structure spectroscopy with X-ray free-electron lasers”, Appl. Phys. Lett. 95, 134102 (2009).A new method to perform X-ray absorption spectroscopy experiments at a free-electron laser has been developed. Instead of selecting a narrow bandwidth of the incident beam with a grating-monochromator, a dispersive set-up is used. The incident pink radiation from the SASE-FEL is dispersed by the grating and collected by an area detector. A special sample-preparation method has been used in order ...
Thomson scattering at FLASH sheds light on fundamental interactions in warm dense hydrogen
Published as: "R.R. Fäustlin et al. Observation of Ultrafast Nonequilibrium Collective Dynamics in Warm Dense Hydrogen", Phys. Rev. Lett. 104, 125002 (2010).The short pulse duration and high intensity of FLASH soft x-ray radiation at DESY allows us to generate and probe highly homogeneous warm dense non-equilibrium hydrogen within a single light pulse. By analyzing the spectrum of the 13.5 nm Thomson scattered light we determine the plasma temperature and density. The results are compared via simulations with different models for impact ...
A tool for studying ultrafast dynamics
Published as: “Performance of a picosecond X-ray delay line unit at 8.39 keV”, Optics Letters 34, 1768–1770 (2009).Although X-ray free-electron lasers provide extremely intense and coherent pulses, their time structure can compromise the applicability of experimental techniques such as X-ray pump/X-ray probe or X-ray photon correlation spectroscopy (XPCS). To fully exploit the potential of XFEL light with the aforementioned techniques we have developed a hard X-ray delay line, i.e. a device capable of splitting a single X-ray pulse ...
The fate of ecotoxic hexavalent chromium in the environment
Published as: “Soil humic acids may favour the persistence of hexavalent chromium in soil”, Environmental Pollution 157, 1862 (2009).Chromium occurs naturally in the Earth’s crust in various oxidation states ranging from 0 to 6+. After entering the soil, hexavalent chromium Cr6+, being a strong oxidant, can be readily reduced to trivalent chromium Cr3+ in the presence of various electron donors, including soil organic matter. Cr3+ readily precipitates or becomes immobilised after sorption onto soil ...
FLASH excites giant atomic resonance
Published as: “Extreme Ultraviolet Laser Excites Atomic Giant Resonance”, Phys. Rev. Lett. 102, 163002 (2009).FLASH produces the highest irradiance of extreme ultraviolet (EUV) and soft X-ray pulses in the world. When these pulses are focused even further by a spherical multi-layer mirror developed for EUV lithography, the levels of irradiance can reach 1016 W cm-2 [1]. The mechanism of light-matter interaction is not very well understood at these wavelengths and extremely high irradiance levels and needs to be ...
From morphological to functional analysis of the cochlear system
Published as:“The cochlea in fetuses with neural tube defects”, Int. J. Devl. Neuroscience 27, 669-676 (2009).
“Pelizaeus Merzbacher disease: morphological analysis of the vestibulo-cochlear system”, Acta Oto-Laryngologica, 99999:1, (2009).
“High-resolution X-ray tomography of the human inner ear: synchrotron radiation-based study of nerve fibre bundles, membranes and ganglion cells”, Journal of Microscopy, Vol. 234, Pt 1, 95-102 (2009).
Microtomography using monochromatic synchrotron radiation (SRμCT) ...
How a gold contact on a conducting polymer film is formed
Published as: “In situ GISAXS study of gold film growth on conducting polymer films”, ACS Applied Materials and Interfaces 1, 353–362 (2009).Almost all applications using conducting polymers require a metal contact. In a typical device, the interface between the polymer and the metal layer is of importance. Here we observe how a gold contact is formed on the conducting polymer polyvinylcarbazole (PVK) during sputter deposition. This growth process was observed in-situ via grazing incidence small-angle X-ray scattering (GISAXS). The ...
Lipid membranes trigger fibril formation of diabetes proteins – red wine compound inhibits fibrillation
Published as: “Elucidating the Mechanism of Lipid Membrane-Induced IAPP Fibrillogenesis and Its Inhibition by the Red Wine Compound Resveratrol: A Synchrotron X-ray Reflectivity Study”, J. Am. Chem. Soc. 131, 9516-9521 (2009).The islet amyloid polypeptide (IAPP) or amylin plays a major role in the pathogenesis of type-II diabetes mellitus (T2DM). Using X-ray reflectivity, atomic force microscopy and infrared spectroscopy in concert, we obtained a molecular picture of how lipid interfaces trigger the fibrillation process and how ...
Voltage induced Ti valence switching in SrTiO3
Published as: “Switching Ti Valence in SrTiO3 by a dc Electric Field”, Phys. Rev. Lett. 102, 087601 (2009)Strontiumtitanate SrTiO3 (STO) is a prototypical perovskite, a class of substances, which find wide applications based on their interesting ferroic properties. STO itself is not ferroic, but it is used as a substrate for many perovskite thin films due to its well matching lattice constant and its chemical inertness. However, STO also has an interesting property: Upon the application of an electric field, structural ...
Revealing the structural dynamics of ultrafast organic switchers
Published as: Time-Resolved X-ray Diffraction of the Photochromic alpha-Styrylpyrylium Trifluoromethanesulfonate Crystal Films Reveals Ultrafast Structural Switching, J. Am. Chem. Soc. 79, 131,15018-15025 (2009).The ultrafast structural dynamics of the [2+2] photocycloaddition of alpha-styrylpyrylium trifluoromethanesulfonate (TFMS) has been studied for the first time at DESY and the ESRF. During the photoreaction, optical and infrared spectroscopy confirms the colour change of alpha-styrylpyrylium (TFMS) crystals making the system to an ...
Resonant magnetic scattering with femtosecond soft X-ray pulses from a free electron laser operating at 1.59 nm
Published as: Resonant magnetic scattering with femtosecond soft X-ray pulses from a free electron laser operating at 1.59 nm, Phys Rev B 79, 212406 (2009)We report on a resonant magnetic scattering experiment using soft X-ray pulses generated from the free-electron laser FLASH at DESY. Using the fundamental wavelength of FLASH at 7.97 nm we were able to detect the 5th harmonic at a wavelength of 1.59 nm with an average energy of 4 nJ per pulse. We demonstrated the feasibility of resonant magnetic scattering at an FEL source by using a ...
Single-shot Terahertz field driven X-ray streak-camera
Published as: “Single-shot Terahertz field driven X-ray streak-camera”, Nature Photonics doi: 10.1038/NPHOTON.2009.160.A few-femtosecond X-ray streak camera for the temporal characterisation of ultrashort X-ray pulses produced by a free-electron laser has been realised at FLASH. In the experiment the electric field of an intense THz pulse is used to accelerate photoelectrons which have been ionised by the FEL pulses. Borrowing its concept from attosecond metrology, the femtosecond X-ray streak camera fills the gap between conventional ...
Creating transparent aluminium with FLASH
Published as: “Turning solid aluminium transparent by intense soft X-ray photoionization”, Nature Physics doi:10.1038/nphys1341.The free-electron laser FLASH at DESY when focussed to ≤1 µm spots reaches record intensities over 1016 W/cm² in the soft X-ray wavelength regime. In an experimental campaign FLASH, at photon wavelength of 13.5 nm, reached these extreme intensities leading to the saturation of the absorption of an L-shell transition in aluminium: the samples become transparent for soft X-rays (at 92 eV photon ...
Coherent x-ray diffraction imaging applied to the determination of 2D crystalline structure with a single pulse train of FLASH
Published as: ''Coherent-pulse 2D Crystallography at Free Electron Lasers'' Phys. Rev. Lett. 102, 035502/1-5 (2009).Crystallization and radiation damage is presently a bottleneck in protein structure determination. We propose to use two-dimensional (2D) finite crystals and ultrashort Free Electron Laser pulses to reveal the structure of single molecules. This can be especially important for membrane proteins that in general do not form 3D crystals, but easily form 2D crystalline structures. We have demonstrated single pulse train ...
A combination of X-ray imaging experiments
Published as: “Combining Synchrotron and Laboratory X-Ray Techniques for Studying Tissue-Specific Trace Level Metal Distributions in Daphnia Magna”, J Anal At Spectrom, 23, 829-839 (2008)What is the effect of transition metals on the health of freshwater invertebrates? One problem is to determine the concentration of trace-level distributions within the organs of the animal, which is the size of a few mm in the case of a typical model system – the water flea Daphnia magna. The combination of 2D/3D fluorescence micro-probe and X-ray ...
Lensless imaging for determining electron density profi les on the nanoscale (in-house research performed at the ESRF)
Published as: “Hard X-Ray Holographic Diffraction Imaging”, Phys. Rev. Lett. 100, 245503 (2008)Nanoscience mandates the ability to characterise the structure of objects on the nanoscale. For several reasons, hard X-rays are very attractive for that purpose: a wavelength in the order of ≈1 Å allows for excellent spatial resolution; the high penetration into matter permits to study thick samples or even buried structures in an easy-to-realise experimental setup; and with the upcoming hard X-ray free-electron lasers the achievable ...
How metallic iron eats its own native oxide
Published as: “How Metallic Fe Controls the Composition of its Native Oxide”, Phys. Rev. Lett. 101 056101 (2008).What happens to an ultrathin film of iron oxide when metallic iron is deposited on top of it? We have investigated this question by X-ray absorption spectroscopy performed in-situ during the deposition process. Typically, the native oxide is a non-stoichiometric mixture of different Fe oxide phases, containing even some Fe atoms in a metallic-like state. Deposition of metallic Fe on such an oxide leads to a reduction of the ...
Study of biologically active molecules from ground-state electron densities
Published as: “A Comparative Study on the Experimentally Derived Electron Densities of three Protease Inhibitor Model Compounds”, Org. Biomol. Chem. 6, 2295-2307 (2008).In order to contribute to a rational drug design with ground-state electron densities, it is important to evaluate the deduced functions and properties that provide information on reactivity. Electrostatic potentials mapped on molecular surfaces and Zero-Laplacian iso-surfaces can be referred to as reactive surfaces because they show centres of nucleophilicity or ...
Structural basis of recognition and activation of mRNA decapping complex
Published as: "Structural basis of Dcp2 recognition and activation by Dcp1", Mol. Cell 29, 337-349 (2008)Small-angle X-ray scattering (SAXS) is rapidly becoming a streamline tool in structural molecular biology providing unique information about overall structure and conformational changes of native macromolecules in solution. Of particular interest is the joint use of SAXS with the high resolution methods like crystallography to study functional complexes. For a Dcp1p-Dcp2n protein complex playing a major role in the process of messenger ...
Frustrated multistep ionization
Published as: “Multistep Ionization of Argon Clusters in Intense Femtosecond Extreme Ultraviolet Pulses”, Physical Review Letters 100, 133401 (2008)The soft X-ray free electron laser FLASH allows for the first time to probe the super intense light pulse – matter interaction at short wavelength, providing the basis for a large variety of studies with femtosecond X-ray pulses. We have performed a photoelectron spectroscopy study complemented with Monte Carlo simulations about the ionization dynamics of atomic clusters at FLASH at ...
Amorphous and non-stoichiometric main group oxide goes metallic
Published as: “A chemically driven insulator–metal transition in non-stoichiometric and amorphous gallium oxide”, Nature Materials Vol. 7, 391-398 (2008)Insulator–metal transitions are well known in transition metal oxides, but inducing an insulator–metal transition in the oxide of a main group element is a major challenge. We succeeded in demonstrating that highly nonstoichiometric, amorphous gallium oxide shows an insulator–metal transition, with a conductivity jump of seven orders of magnitude at a temperature around 670 K. ...
Advanced software assists to expose the hidden world of biological molecules
Published as: “Automated macromolecular model building for X-ray crystallography using ARP/wARP version 7”, Nature Protocols 3, 1171-1179. PMID: 18600222 (2008).ARP/wARP is a software suite to build macromolecular models in X-ray crystallographic electron density maps. Structural genomics initiatives and the study of complex macromolecular assemblies and membrane proteins rely on advanced methods for 3D structure determination. ARP/wARP 7.0 meets these needs by providing the automated tools for: iterative protein model building ...
Mechanical Properties of Silk: Interplay of deformation on macroscopic and molecular length scales
Published as: “Mechanical Properties of Silk: Interplay of Deformation on Macroscopic and Molecular Length Scales”, Phys. Rev. Lett. 100, 048104, (2008)Using an in situ combination of tensile tests and X-ray diffraction, we have determined the mechanical properties of both the crystalline and the disordered phase of the biological nanocomposite silk by adapting a model from linear viscoelastic theory to the semicrystalline morphology of silk. We observe a strong interplay between morphology and mechanical properties. Silk‘s high ...
The many faces of molecular assemblies in electronic devices
Published as: “Orientation-dependent ionization energies and interface dipoles in ordered molecular assemblies”, Nature Materials 7, 326 - 332 (2008)Organic molecules provide fascinating possibilities for fabricating inexpensive novel electronic devices, organic light-emitting diodes, and flexible environmentally-friendly low-cost solar cells [1]. The efficiency of organic solar cells depends on the chemistry of the materials employed and critically on the electronic ...
Massively parallel X-ray holography - Taking a leaf from astronomy to reach the nanoscale
Published as: “Massively parallel X-ray holography", Nature Photonics 2, 560–563 (2008)The ultrafast pulses from short-wavelength free-electron lasers (FELs), such as FLASH, give us the possibility for imaging processes on the timescale of atomic motions. The upcoming X-ray FELs such as Linac Coherent Light Source and European XFEL will additionally allow us to probe dynamic processes approaching inter-atomic length scales. For many such experiments it is necessary to extract spatially-resolved information from a single pulse since ...
Visualizing a Lost Painting by Vincent van Gogh using X-ray Fluorescence Mapping
Published as: "Visualization of a lost paintig from Vincent van Gogh using synchrotron-radiation based X-ray fluorescence elemental mapping"Many paintings by Vincent van Gogh cover a previous composition, because the artist frequently re-used the canvas of abandoned paintings. Using synchrotron induced X-ray Fluorescence mapping we visualized a woman’s head hidden under the work Patch of Grass. The resulting elemental distributions and additional X-ray absorption spectroscopy on selected points on the painting enabled an ...
Cooperative or Self-centred: Can an electron make the choice?
Published as: “Localization and loss of coherence in molecular double-slit experiments“ in: Nature Physics, VOL 4, 649-655 (2008)
Nitrogen molecules were irradiated with soft x-rays over a wide energy range. Because of this irradiation electrons are emitted from the molecule with a kinetic energy that depends on the choice of photon energy. This means slow or fast, where the velocity determines the resolving power of the electron for its environment. The researchers succeeded in demonstrating that there is a transition ...
Ultrafast Movies of Nanoscale Dynamics
Published as: “Ultrafast single-shot diffraction imaging of nanoscale dynamics”, Nature Photonics 2, 415–419, (2008).
Combining an optical laser with FEL pulses from FLASH in a pump-probe set-up enables imaging with high temporal and spectral resolution. A nanostructure is ablated by an optical laser and this process is followed with lensless coherent diffractive imaging using FLASH pulses. A spatial resolution of better than 50 nm is achieved. By taking pictures of a succession of exploding targets, a movie can be made ...
Characteristics of picoliter droplet dried residues as standards for direct analysis techniques
Published as: U.E.A. Fittschen et al., Anal. Chem. (2008), 80, 1967-1977
Nowadays microscopic analysing techniques are easily capable of resolution of a few micrometers and beyond. The accuracy of the techniques rely on the comparison to standard reference material. However, reference materials which are homogeneous on the micrometer-scale are often not available or tedious to prepare. In contrast the preparation of dried residues derived from pico liter volumes using ...
Transverse coherence properties of X-ray beams in third-generation synchrotron radiation sources
| Published as: | [3] G. Geloni, E. Saldin, E. Schneidmiller, M. Yurkov, Opt. Comm. 276, 1, p. 167 (2007) and [4] G. Geloni, E. Saldin, E. Schneidmiller, M. Yurkov, Nucl. Instr. and Methods in Phys. Res. A, 588, 3, 463(2008) |
In recent years, continuous evolution of synchrotron radiation (SR) sources has ...
A femtosecond X-ray/optical cross-correlator: FLASH X-ray pulse induced transient changes of the optical reflectivity
Published as: C. Gahl et al., Nature Photonics 2, 165-169 (2008)For a fundamental understanding of ultra fast dynamics in chemistry, biology and materials science it has been a longstanding dream to record a molecular movie, where both the atomic trajectories and the chemical state of every atom in matter is followed in real time with time resolved pump/probe spectroscopy. X-ray free-electron lasers (FEL) provide this perspective as they deliver brilliant femtosecond X-ray pulses spanning a wide photon energy range. To cross-correlate and ...
Vacuum ultraviolet 5d-4f luminescence of Gd3+ and Lu3+ ions in fluoride matrices
Published in Phys. Rev. B 75, 075111 (2007)Research on new optical materials is fundamental for the development of various applications, such as laser systems, plasma TVs, or new detectors for medical diagnosis. Many of these materials make use of ions of rare earth elements (RE), which can absorb and emit light in the ultraviolet and visible wavelength range efficiently.
In our work, we have focused on the luminescence and excitation properties of 5d-4f transitions of gadolinium (Gd3+) and lutetium ...
Control of magnetic anisotropy in (Ga,Mn)As by lithography-induced strain relaxation
Published as: J. Wenisch et al., Phys. Rev. Lett. 99, 077201 (2007).Controlling the magnetic properties of semiconducting materials is certainly one of the key issues in the field of modern electronic device technology. An important material system in this context is (Ga,Mn)As, which has been the focus of many studies over the last years. As the understanding of its complex transport and magnetic properties increases, the focus of interest shifts from basic research towards its application in devices. For this, it is necessary to obtain a ...
Order causes secondary Bragg-peaks in soft materials
Published as: S. Förster et al., Nature Materials 6, 888 (2007)Shear forces are one of the most widely used methods to order and align soft crystals. Small-angle x-ray and neutron scattering experiments revealed for the first time the detailed structure of soft crystals. In particular, such crystals exhibit Bragg-peaks that were difficult to index assuming homogeneous crystal structures. Their origin had been attributed to changes in the crystal structure that are induced by the shearing process. We demonstrate that these Bragg-peaks ...
Assessing the Origin and Fate of Cr, Ni, Cu, Zn, Pb, and V in an Industrial Polluted Soil by combined Microspectroscopic Techniques and Bulk Extraction Methods
Published as: R. Terzano et al., Environ. Sci. Technol., 41, 6762-6769.It is commonly recognized that soil is the major sink for heavy metal (HM) contaminants released into the environment by human activities and that the mobility, bioavailability and toxicity of metals strongly depend on their solubility and therefore on their geochemical forms. Soils contaminated with HM can cause serious risks to human health, e.g. if vegetables cultivated on contaminated soils are consumed. The correct identification of HM chemical forms in soil is ...
Biological Systems as Nanoreactors: Anomalous Small-angle Scattering Study of the CdS Nanoparticle formation in multilamellar Vesicles
Published as: A. Bóta et al., J. Phys. Chem. B, 111 (8), 1911 (2007).The formation of the cadmium sulfide (CdS) particles in the gaps between the stacks of bilayers inside multilamellar vesicles is described illustrating a new pathway in the preparation of nanometer-scale particles. The in situ structural characterization of both the CdS particles and the vesicles as reaction medium was performed in the early and final states of the process by using anomalous small-angle X-ray scattering (ASAXS) and freeze-fracture methods. The ...
X-ray Diffraction Studies on Multiferroic TbMnO3 and DyMnO3 in High Magnetic Fields
Published in : Phys. Rev. B 75, 212402 (2007), Phys. Rev. B 75, 020101(R) (2007), Phys. Rev. B 73, 020102(R) (2006)Multiferroic compounds are materials that exhibit two or more switchable states, such as polarization, magnetization or strain which are again interdependent from each other. Magneto-electric multiferroics have recently attracted a lot of interest due to the exceptional properties which allow the control of spontaneous ferroelectric polarization by applied magnetic fields, ultimately leading to new types of magneto-electric ...
Two-color photoionization in xuv free-electron and visible laser fields
Published in: Physical Review A 74, 011401(R) (2006)The Free electron LASer in Hamburg (FLASH) is a unique source for intense, ultra-short extreme-uv (xuv) light pulses. In view of these unprecedented characteristics, an associated time-synchronized optical laser facility opens up new and particularly exciting research opportunities. First characterization of this pump-probe set-up was obtained recently via time-dependent two-photon experiments on rare gases. The process of above threshold ionization (ATI), which is very sensitive to the ...
Large-area ordered polymeric nanochannel arrays - a high-resolution investigation
Published in: Appl. Phys. Lett. 88, 083114 (2006)Large scale arrays of polymer nanochannels are important tools for many applications, such as micro-fluidics and fabrication of bioanalytical assays. Polymer nanochannels are defined as the alignment of polymeric material in walls with negligible interconnection in perpendicular direction. We present here a new, unexplored route to create such polymeric arrays. Their large-scale order as well as their orientation with respect to the underlying substrate is probed using high-resolution ...
Ultrafast Coherent Diffractive Imaging at FLASH
Published in: Nature Physics 2, 839 (2006)Using the FLASH facility we have demonstrated high-resolution coherent diffractive imaging with single soft-X-ray free-electron laser pulses [1]. The intense focused FEL pulse gives a high resolution low-noise coherent diffraction pattern of an object before that object turns into a plasma and explodes. Our experiments are an important milestone in the development of single-particle diffractive imaging with future X-ray free-electron lasers [2,3]. Our ...
Novel ferroelectrics phases by strain engineering
Published as: G. Catalan et al., Phys. Rev. Lett. 96, 127602 (2006)Ferro-piezoelectrics are the active elements in a very large number of applications from gas lighters to alarm buzzers. Their properties arise from the presence of a spontaneous polarization. Thin films of the classical ferroelectric PbTiO3 subjected to a small tensile strain have been successfully grown unit-cell-by-unit-cell and investigated by using x-ray diffraction. This work demonstrates that i) controlling the growth of thin films at the atomic level ...
2D-mapping of the structure of a heterogeneous catalyst inside a catalytic microreactor during the partial oxidation of methane
Published as: J.-D. Grunwaldt et al., J. of Phys. Chem. B 110, 8674 (2006)Structure-activity relationships gained by studying catalysts at work are considered the key to further development of homogeneous and heterogeneous catalysts. In situ X-ray absorption spectroscopy (XAS) is a well-established technique to study catalytic reactions, since it can monitor chemical states of both crystalline and X-ray amorphous structures even in gas phase, liquid phase or at high pressure. However, spatial variation of the structure within a catalytic ...
X-ray tomographic imaging of atoms - crystal views from inside
Published as: P. Korecki et al., Physical Review Letters 96, 035502 (2006)Conventional x-ray crystallographic methods, which are used for almost 100 years, detect x-rays diffracted by the crystal planes. In a recent paper it was demonstrated that the atomic structure can be imaged directly from real-space projections sensed by absorbing atoms inside a crystal. The use of white x-rays allowed neglecting the diffraction effects and treating the x-ray beam as a searchlight which directly produces x-ray projections of the main atomic planes ...
Anchoring of the giant muscle protein titin in muscle cells
Published as: P. Zou et al., Nature 439, p. 229 (2006)The Z-disk of striated and cardiac muscle sarcomeres provides the architectural framework to assemble and anchor the largest known muscle filament systems by an extensive network of protein-protein interactions. High resolution X-ray diffraction data unravel how the N-terminus of the longest filament component, the giant muscle protein titin, is assembled into an antiparallel (2:1) sandwich complex by the Z-disk ligand telethonin. The structure provides a molecular paradigm of how ...
A molecular double-slit experiment with partial “which-way” information
Published as: D. Rolles et al., Nature 437, p. 711-715 (2005)One of the most counterintuitive aspects of quantum physics is that for some scenarios which are perceived as “either or” in everyday life, there is also the "as well as" possibility. A natural example of such behaviour, however, has now been seen in molecular nitrogen where each electron, even a highly localized core electron, is on both atoms of the molecule at the same time. When the molecule is ionised, this gives rise to coherent electron emission from both ends of the ...
Puzzling the Ribosome
Published as: M. Diaconu et al., Cell 121, 991-1004 (2005)Genomes of rather divers species like humans, mice or worms have been found to be amazingly similar. In these and all other organisms, the genetic information is translated by the ribosome, in a way that the small but crucial differences are accurately maintained. To understand how the ribosome works, and how antibiotics block specifically bacterial ribosomes, molecular structures of the ribosome and the related co-factors are essential. In a collaborative study employing ...
Diamond clusters show limitations of the quantum confinement model
Published in: Physical Review Letters 95, 113401 (2005)Clusters and nanocrystals are of great scientific and technological interest due to their size dependent properties. Changes in their electronic structure have been successfully described with the quantum confinement model, which predicts increasing band gaps with decreasing particle sizes due to shifts of the band edges towards higher energies. Now, soft x-ray absorption measurements of diamond clusters show that the bulk-related unoccupied density of states do not exhibit any such ...
Temperature dependence of isotopic quantum effects in water
Published in: Physical Review Letters 94 (2005) 04780Water is the most important liquid on earth and it may be surprising therefore that water still keeps some of its secrets. The average static properties of a system of molecules, such as pressure or the average structure, should at a given temperature not depend on the total mass of the molecules or the mass distribution if the interaction is classical. Contrary to that expectation, isotopic forms of water, ...
Ribosome Recycling and Termination of Protein Synthesis
Published in: Embo J. 24(2) 251-260, 2005The ribosome deciphers and translates the genetic code in all living organisms. This process - termed protein biosynthesis – requires several co-factors accelerating or catalyzing various steps. Termination is the last step of protein biosynthesis and requires the combined action of the Ribosome Recycling Factor (RRF) and the Elongation Factor G (EF-G). We recently determined the crystal structure of RRF bound to Deinococcus radiodurans 50S subunit at 3.3 Å resolution. These results provide a ...
Evidence for Pearl-Necklace Structure in Aqueous Solution of Polyacrylate Chains with Sr2+-Counterions
Published in: Europhys. Lett., 66 (3), pp. 331-337 (2004)Polyelectrolytes are highly charged macromolecules. A large variety of such systems, where the role of electric charge is essential for the structure and proper functioning has been discovered in nature like for instance nucleic acids, numerous enzymes or self assembling proteins. Due to the high charge density, concentrated on the chain, polyelectrolytes show a strong interaction between the segments of the same chain and other macromolecules as well as they exhibit a ...
Probing active sites during palladium-catalysed alcohol oxidation in “supercritical” carbon dioxide
Published in: Catalysis Letters 90, 221-229, 2003 and Catalysis Today 91-92, 1-5, 2004Supercritical fluids have recently attracted considerable attention in catalysis, extraction, separation, crystallization, and polymer technologies due to their unique physical properties. Although they have led to better catalytic performance in a number of heterogeneously catalysed reactions, fundamental understanding is still lagging behind and necessitates in situ spectroscopic studies at high pressure. For the first time, a heterogeneous catalyst ...
Precise measurement of the lattice parameters of sapphire in the temperature range 4.5 -250K using the Mössbauer wavelength standard
Published in: J. Appl. Cryst. 36, part 4, 1075-1081 (2003)The lattice parameters of sapphire (α-Al2O3) have been measured in a temperature range from 4.5K to 250K with a relative accuracy of better than 6 x 10-6. Sapphire is a potential new material for X-ray crystal optics, especially attractive in applications as Bragg back-scattering mirrors since it allows unlike silicon exact Bragg back-scattering with high reflectivity for X-rays in the 10-50 keV spectral range. However, lattice parameters ...
Charge density analysis of YBa2Cu3O6.98. Comparison of theoretical and experimental results
Published in: Acta Cryst. A59, 437-451, 2003Charge density investigations play an important role in order to determine the crystalline and electronic structures of materials. Theoretical models are usually tested by experimental data, but up to now this was difficult for high-Tc superconductors. Using high-energy synchrotron radiation, structure factors of YBa2Cu3O6.98 were measured at lambda = 0.124 A. Experimental and theoretical results generally agree well. A topological analysis shows that ...
Topography for Independent Binding of Two Different Ligands to a Peroxisomal SH3 Domain
Published in: Mol. Cell 10, 1007-1017, 2002While the function of most small signalling domains is confined to binary ligand interactions, the peroxisomal Pex13p SH3 domain has the unique capacity of binding to two different ligands, Pex5p and Pex14p. We have used this domain as a model to decipher its structurally-independent ligand binding sites. By the combined use of X-ray crystallography, NMR spectroscopy and circular dichroism, we show that the two ligands bind in unrelated conformations to patches located at opposite surfaces of ...
Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser
Published in Nature 420, 482 (2002)Fourth-generation light sources based on free-electron lasers (FEL) will be a source of intense, short-wavelength radiation for a range of applications, including biological imaging. The first results reported on December 5, 2002 in Nature, from experiments with the FEL at the TESLA test facility at DESY shed light on the interaction of short-wavelength, short-pulse radiation with matter. Here, unexpectedly strong absorption of the laser radiation by Xenon clusters was observed, resulting in the ...
Quadrupolar transitions detected by resonant Auger spectroscopy
Published in: Phys. Rev. Lett. 88, 243001, June 17, 2002Quadrupolar transitions can play an important role in X-ray absorption spectroscopy, especially when it is used for magnetic measurements, like in X-ray Magnetic Circular Dichroism or Resonant Magnetic Scattering. We show here that resonantly excited Ti KL2,3L2,3 Auger spectra of TiO2(110) carry a clear signature of quadrupolar transitions from the 1s to localized eg and t2g d-like states. The quadrupolar nature of the observed additional ...
Chiral Amplification of Oligopeptides in Two-Dimensional Crystalline Self-Assemblies on Water
Published in: Science, Vol. 295, Issue 5558, pp. 1266-1269, February 15, 2002Many organic molecules are chiral: Their S and R (left- and right-handed) enantiomers are non-superimposable mirror images of each other. Chemical reactions by default yield racemic mixtures consisting of 50:50 R and S enantiomer. However, in Nature proteins consist of only S-amino acids and RNA and DNA contain only R-sugars. This break of symmetry may have occurred through the amplification to 100% of a slight initial imbalance. In this study, an amphiphilic ...
