Angle-resolved photoemission studies of Pb films prepared on atomically uniformAg(111) films reveal a striking Fabry-Pérot-like behavior typical of a high-finessePb/Ag/Si(111) electron interferometer. Remarkably, the quantized electronic structure of the underlying Ag films persists despite Pb overlayers much thicker than the photoemission escape depth and an incommensurate Pb/Ag interface. Comprehensive simulations clearly illustrate the manifest coherence of the electronic structures, permitting the characterization of the deeply embedded Ag quantum well. This demonstrated exploitation of electronic coherence will prove useful to applications requiring non-invasive access to buried structures.
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Two-dimensional ultrathin films often exhibit properties dramatically different from their three-dimensional bulk counterparts, due to quantum confinement effect in reduced dimension. In this talk, I will first present our recent study of electronic properties of epitaxial graphene layers, using angle-resolved photoemission spectroscopy (ARPES) with variable light polarizations. Our results demonstrate that the "chiral" electronic states in this two-dimensional system can be unambiguously revealed by this technique. Next I will report our current research progress in quantum confinement effects in ultrathin films of topological insulators (TIs), using ARPES and surface X-ray scattering (SXS). Due to a largely enhanced surface-to-bulk ratio, TI ultrathin films are considered to be a very promising system for practical applications of TIs. It is therefore crucial to understand how the electronic and structural properties in TI thin films converge to their bulk limits. For ultrathin Bi2Te3 films grown on Si(111), we found that the topological surface state converges to its bulk form already at 4 quintuple layer, in remarkable agreement with theoretical prediction for a freestanding film. Our surface X-ray study confirms that the quasi-freestanding Bi2Te3 films are achieved through a buffer layer between the film and substrate, which effectively saturate the dangling bonds of the Si(111) substrate. Finally, if time permits, I would also like to present our recent results on the novel tri-layer growth of ultrathin indium films, using ARPES and SXS.
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Complex fluids which encompasses colloidal and nanoparticle suspensions, polymers, nanocomposites, gels, emulsions, etc. exhibit rich viscoelastic behavior over hierarchical structural length scales and a wide range of dynamical time scales. Typically the bulk rheology in such systems are of importance for potential applications. X-ray photon correlation spectroscopy has been successfully used to probe nanoscale dynamics in such systems. In this talk, I will present a few science cases that aim at connecting the motion at nanoscale with bulk rheological properties.
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The development of next generation medical and industrial x-ray analysis techniques have been hindered by a paucity of photon flux emitted by laboratory-based x-ray sources. To address this, GE has developed a class of vacuum-compatible multilayer x-ray photonic devices that, in theory, can concentrate up to 2π steradians of high-energy photons (>60keV) from a laboratory source and redirect them into pre-specified spatial and spectral beam shapes. In this presentation, the theoretical design of these photonic devices, which require x-ray reflectivities (XRR) better than 99.9% from the multilayer components, will be discussed. High-energy experimental XRR data on these unusually high-reflectivity multilayers will be shown. During the development of these x-ray photonic devices, x-ray reflectivity and diffraction were performed with GE’s sensitive, high-dynamic range, digital x-ray detectors. These non-medical applications presented different imaging requirements than the medical applications for which the detectors were originally designed and manufactured. This presentation will also contain a discussion on the detector design and how to take advantage of it to obtain optimal detector performance at low (~8keV) and high (~60keV) x-ray energies for x-ray diffraction and other x-ray imaging
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Relative to space, the dimension of time has been underexploited in x-ray science. Interesting phenomena span a hierarchy of time scales, and the advent of new x-ray facilities bring a broad range of capabilities. The goal of this workshop is to assess the worldwide portfolio of x-ray sources and identify classes of experiments best done at complementary facilities (synchrotrons and FELs) so that researchers can be informed about present and planned capabilities. Attendees will "brainstorm" about potential time-resolved experiments in materials; chemistry; condensed matter physics; atomic, molecular, and optical physics; and more. A summary report will be prepared.
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Pizza will be served
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The 4d and 5d transition metal oxides exhibit many exciting phenomena like ferroelectricity, ferromagnetism, antiferromagnetism, meta-magnetism, metal-insulator transition and superconductivity. The ruthenium and iridium oxides are expected to be more metallic and less magnetic than the 3d and 4f oxides because of the extended nature of the 4d and 5d orbitals. In marked contrast, many ruthenates and iridates are magnetic insulators that exhibit a large array of phenomena not usually seen in other materials. In this talk, I focus on the anomalous physical properties and novel phenomena exhibited by these materials. These include novel borderline magnetism and spinvalve effect in ruthenates, and a novel Je_eff= 1=2 insulating state inthe iridates.
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The Linac Coherent Light Source (LCLS) at SLAC has been the first x-ray Free Electron Laser (XFEL) in operation. By providing x-ray pulses with incomparable peak brightness, it opened a new era in x-ray physics. Typical characteristics, available from the soft x-ray to the hard x-ray region (500eV-10000eV), amount to approximately 1012 photons per pulse, in a time believed to be as short as a few tens of femtoseconds (10-15 s). Measuring the exact pulse duration of the x-ray pulses has been a challenge from the start, due to a lack of existing techniques capable of accessing that information. The situation is rendered even more complex by the fact that LCLS lasing is based on SASE (Self Amplified Stimulated Emission), which essentially means that every pulse starts from random noise, producing in the end a purely chaotic source. Ideally, a pulse duration characterization requires a single shot measurement capability. While a lot can be learned from measurements done on the electron beam, as well as from a statistical analysis of the pulse energy and high-resolution spectrum of x-ray pulses, ultimately it is necessary to measure each x-ray pulse itself. I will present attempts to realize that by using the technique known as laser streaking, where photoelectrons released during ionization of a gas target see their final energy modified by a simultaneously present short infrared or terahertz pulse.
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We present the developments on diffractive X-ray optics achieved during the last year at the APS and CNM. Among other results, we demonstrate hard X-ray full-field transmission microscopy with sub-25 nm spatial resolution and tomographic capabilities. We discuss future developments and improvements.
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Abstract:

The field of X-ray surface scattering has blossomed over the past thirty years in large part because of the incredible advances in source brightness provided by facilities such as the Advanced Photon Source. Similarly, x-ray microscopy has been driven by improvements in x-ray sources and optics. In this talk, I will use examples from my own research to highlight improvements in both these areas. Finally, I will discuss the new possibilities for interface studies enabled by the beam line and capabilities that will be built at the upgraded APS. The upgraded APS will enable researchers the opportunity to study surfaces and interfaces in both real and reciprocal spaces, and will bring new insights to this important area of science.
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The aim of this talk is to describe the recently rebuilt surface diffraction beamline of the European Synchrotron Radiation Facility in Grenoble, France, and to provide some examples of the activities carried out. Particular attention will be dedicated to the most recent studies of operando heterogeneous catalysis. A new flow reactor [1], which we have conceived, gives the possibility of performing in-situ studies of the structure and morphology of the catalyzer surface at atmospheric pressure and at high temperatures. Results concerning the CO oxidation on Pd will be shown in details [2,3] together with examples of other reactions.

[1] R. van Rijn, et al., Rev. Sci. Instrum. 81 (2010) 014101
[2] R. van Rijn, et al. Physical Chemistry - Chemical Physics 13 (2011) 13167
[3] B.L.M. Hendriksen, et al., Nature Chemistry 2 (2010) 730
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We will describe the optical design of four beamlines: IRENI, CSX, ISR and FXI. IRENI is an infrared beamline collecting 300 mrad of a bending magnet at SRC and dedicated to FTIR micro-spectroscopy. CSX is the only soft x-ray beamline in the NSLS-II project. It consists of two independent branches covering the energy range 170-2000 eV, one for experiments requiring high coherent flux and the other for fast polarization experiments. The source for CSX are two undulators working either phased or canted. ISR and FXI are two of the second phase beamlines for NSLS-II. The former is based on an undulator and is designed for In-Situ and Resonant Hard X-ray Studies in the energy range 2.1-2.3 keV. The source for FXI is one of the NSLS-II damping wigglers. FXI will be dedicated to Full field X-ray Imaging using an existing x-ray microscope at NSLS.
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The European Synchrotron Radiation Facility is presently undergoing an important upgrade program. Within this upgrade, eight new beamlines will be constructed and will become operational between 2012 and 2016. One of the first upgrade beamlines (UPBL) is UPBL11, designed to provide state-of-the-art conditions to perform time resolved and extreme conditions x-ray absorption spectroscopy.

UPBL11 hosts two energy dispersive x-ray absorption spectrometers coupled to two experimental stations, and will become fully operational in 2012. This instrument will provide the user community new opportunities for investigating matter at extreme conditions of pressure, temperature and magnetic field. Target experiments for the future include kinetic studies of chemical reactions at high pressure and temperature, and investigation of extreme states of matter that can be maintained only over very short periods of time.

In this presentation, I will make an overview of recent results obtained on the former energy dispersive XAS beamline ID24 in the area of extreme conditions. Examples cover studies of chemical reactions that occur in the interior of planets, the investigation of pressure induced collapse of ferromagnetism in 3d metals, and first attempts to probe the electronic and local structure in melts at high pressures. Future perspectives for the investigation of laser-shocked matter are also discussed.
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Inline X-ray phase contrast is an attractive contrast mode for X-ray imaging techniques due to its increased sensitivity: by leaving an appropriate drift space between the sample and the imaging detector, interfaces within the probed specimen can be visualized. While this information is often useful for visual inspection, any further quantitative is not easily possible: the gray levels within the different materials regions are not necessarily different; they are just varying at the interfaces. But if the transmission radiographs are sent through a phase-retrieval process, the tomograms will exhibit ‘area contrast’ rather than edge-enhancing contrast.

In this presentation, the implementation and application the single-distance phase retrieval approach will be introduced [1, 2]. Advantages of this method are that it can be applied to any inline phase contrast tomographic data set; it allows phase-sensitive imaging without modification of existing experimental installations; it is extremely robust and user friendly; it can handle data from arbitrarily absorbing (multi-constituent) samples as well as tolerates polychromatic illumination. The latter is of crucial importance to progress towards higher data acquisition rates: when operating without monochromators, i.e. so-called pink beam or white beam configurations, the required exposure times can be reduced drastically. Microtomography in combination with pink-beam illumination and Paganin phase-retrieval has become the most demanded configuration at the ESRF beamline ID19: it covers now 30% of the ID19 data processing and about 80% for palaeontological studies.

[1] D. Paganin, et al., "Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object," J.Microsc. 206 (1), 33 (2002).
[2] T. Weitkamp, A. Rack, et al., "ANKAphase: software for single-distance phase-retrieval from inline X-ray phase contrast radiographs," J. Synchrotron Radiat. 18 (4), 617 (2011).
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The Scientist' s Guide to Optimization has a few things to say on the subject of optimization. Optimization, it says, is about the most massively useful tool a scientist can have. Many design, data analysis, and operational problems can be formulated as optimization problems. We present a survey of current research trends in optimization motivated by applications of relevance to the APS. We will touch on applications such as accelerator design, image analysis, and optimal control. In all cases we will highlight the relevant software projects within Argonne' s Mathematics and Computer Science Division.
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Various scales of spatial and temporal dimensions are involved in catalyst synthesis, reactivity and deactivation. Full understanding the catalytic processes and ultimately controlling the catalytic reactions require probes of broad time and length scales. We have combined multiple X-ray techniques and other spectroscopic techniques to study catalyst synthesis, reactivity and deactivation. Two examples will be presented to demonstrate the power of X-ray and combination of scattering and spectroscopy techniques.

First example is using the time resolved pair distribution function (PDF) methods to probe the kinetics, mechanism, and energetics for Ag nanoparticle synthesis in a porous zeolite. Understanding the formation of nanoparticles and how they are influenced by a support, is critically important for optimizing their activity. The PDF method can provide the nanoscale structure detail and fast time resolution which allows a multi-step mechanism delineated, and rate constants and activation energies to be estimated for reduction and surface diffusion steps. Complimentary diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in situ X-ray absorption near edge spectroscopy (XANES) were used to illustrate the surface functional group and oxidation state changes in the particle formation and growth process.

Second example is about probing the active sites in Ni2P and NiFeP for catalytic hydrodesulfurization (HDS) reaction of a model compound 4,6-dimethyldibenzothiophene (4,6-DMDBT). HDS of 4, 6-DMDBT is dominated by two pathways, hydrogenation (HYD) and direct desulfurization (DDS). EXAFS analysis reveals that HYD is due to the square pyramidal Ni(2) and DDS is due to the tetrahedral sites Ni(1) for Ni2P. Combination of EXAFS and IR suggests the substitution of Fe atom in the active phase and a ligand effect on Ni sites.
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Ultrafast, time-resolved, laser-pump, x-ray-probe experiments are powerful tools for understanding and controlling the behavior of matter at the molecular level. Transient structural changes, both geometric and electronic, of single molecules after excitation by a laser pulse can be probed with high resolution and within complex or disordered environments, such as gases and liquids, taking advantage of the superior spatial resolution, elemental specificity and penetration power of x-rays.

Third generation synchrotron sources, particularly the APS, provide x-rays with a unique combination of properties that are well suited for precision time-resolved measurements which include a high flux (1013 photons/second/0.01% bandwidth) that is distributed in short pulses (~100 ps) with moderate intensity (~106 photons/pulse) at a high repetition rate (MHz). Over the last decade laser-pump, x-ray-probe studies have been carried out at synchrotrons but a major challenge has been the low repetition rate (kHz) of standard amplified lasers resulting in underutilization of the synchrotron’s high flux. In response to this we have implemented a high repetition rate (54 kHz – 6.52 MHz), high power (10 W), laser system at 7ID-D at the APS.

In this talk I will highlight our initial experiments using this laser and the x-ray microprobe at 7ID-D. These include x-ray absorption spectroscopy (XAS) of the metalloporphyrin molecule Ni(II)-tetramesitylporphyrin (NiTMP) in solution at 135 times the rate of previous experiments, combined XAS, x-ray emission spectroscopy (XES), and liquid scattering measurements on the spin-crossover molecule Iron(II)-tris(2,2’)-bipyridine ([Fe(bpy)3]2+) in solution using the full flux available at the APS, and XAS of the photodetachment and recombination of the haloalkane CH2BrI in solution. Our results demonstrate how the use of high repetition rate, short pulse lasers as pump sources can dramatically enhance the duty cycle and efficiency in data acquisition and hence capabilities at synchrotron sources. These techniques will play an important role in the utilization of the SPX, the ~1 ps x-ray pulse source planned in the APS upgrade.
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Abstract Zirconium alloys are of importance to the nuclear industry, with primary application as a structural material for the in-reactor environment. The formation of brittle hydrides within zirconium alloys results in a degradation of the mechanical properties of the component in which they form. Therefore, the characteristics of hydride formation and the subsequent impact of these hydrides are critical factors in the determination of zirconium component service life. This talk summarizes a series of three experimental efforts characterizing the mechanical behavior of hydrides in zirconium alloys with high energy synchrotron X-ray diffraction. Part I focuses on the mechanical response of zirconium hydride within a bulk Zircaloy-2 matrix. Part II studies the near crack tip behavior of unhydrided Zircaloy-2. Part III characterizes the behavior of notch tip hydrides. The aim of this work is to quantify the influence of hydrides on the local notch tip strain field and characterize the internal strains in the hydrides themselves.

* Work conducted while Matthew Kerr was a graduate student at Queen’s University and does not reflect a position of the US NRC.
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The High Energy Diffraction Microscopy (HEDM) program attracts a growing community to the Advanced Photon Source 1-ID beamline. High-energy x-ray diffraction (above 50 keV) has been demonstrated to be a powerful tool for the structural characterization of polycrystalline bulk materials measuring the crystallographic orientation and stress states on the grain and sub-grain scales. High energy tomography provides fast three-dimensional maps using absorption or phase contrast, with spatial resolution at the micrometer scale. Both of these techniques have garnered increased interest towards engineering and industrial applications due to their combination of bulk penetration and high sensitivity.In the presentation I will introduce my HEDM evaluation program DIGIgrain that has been adopted for several user measurements at 1-ID and has proven to provide unique quality, compared to other existing programs, for peak segmentation and data reduction. Case studies of far-field diffraction measurements on metallic and non-metallic materials which have utilized DIGIgrain will also be presented.

The combination of these two complementary contrast mechanisms is highly beneficial for the characterization of inhomogeneities such as cracks or voids. Several case studies will be presented to demonstrate their capability to reveal structural details that cannot be detected by a single technique alone. This is especially true for the near field diffraction technique, which can advance directly by combining tomographic reconstruction and crystallographic orientation mapping from the same data set. This approach enables in situ investigations and avoids the registration problem of independent data sets.
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Although heterogeneous catalysts are widely used among industrial processes, the detailed understanding of catalytic mechanisms still needs deeper investigations. The nature of the active sites, their geometry and local environment are determining parameters for the catalytic performances. A fine characterization is thus required to understand this structure-activity relationship and generally involves spectroscopic techniques, particularly through in situ and operando approaches. To this end, relevant developments regarding the use of time-resolved spectroscopies have been recently achieved. In this context, the formation of active phases and their further evolution under real catalytic conditions will be discussed on the basis of recent studies performed at the French Synchrotron SOLEIL using X-ray absorption spectroscopy and complementary techniques such as Raman spectroscopy. Examples will be detailed to illustrate the characterization of various materials, including supported oxides or metals, which are of wide interest in the area of energy, e.g. for biomass valorization or fuels synthesis.
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Ruthenium and Osmium polypyridyl complexes and their derivatives have attracted increasing interest and have been used as photosensitizers in solar-cells, molecular electronics and light emitting devices. Photoexcitation of those photosensitizers leads to long lived metal-to-ligand charge transfer (MLCT) states. If bonded to proper semiconductor nanocrystals, the photoexcited Ru and Os complexes inject electrons to semiconductors, resulting in interfacial-charge transfer state. We have applied time-resolved X-ray spectroscopy to study the electronic and molecular structures of photosentizers in both MLCT excited state and charge-separated state. A series of Ruthenium and Osmium polypyridyl complexes have been studies. Experimental results were compared with simulations/theoretical calculations, quantitative information on the molecular structure, electronic configuration and molecular orbital energies of ground and excited states have been revealed. The chances in the Ru-ligand distances have been directly characterized and rationalized by the interplay between two important factors governing the metal to ligand bonding, steric hindrance and π-backbonding. These works have demonstrated the great potential of time-resolved X-ray spectroscopy to study fundamental structural-functional correlations in solar electricity and fuel generation for both homogenous systems and heterogeneous interfacial systems.
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Diverse optics fabrication activities are currently underway within the Optics Fabrication Group at NSLS-II, including work on crystal optics, multilayer Laue lens (MLL) growth and sectioning, and reflective multilayer optics. Crystal optics production capabilities currently include orientation, slicing, dicing, lapping, etching, and CMP polishing of silicon for high-resolution IXS, channel-cut monochromators, and other applications. The current status of MLL fabrication will be presented, including partial-nitrogen reactive sputtering for stress and interfacial roughness reduction which has recently led to a 70 micron thick single-growth MLL. Significant effort has been focused on the achievement of highly-stable nitrogen gas mixing for multilayer growth and the problems faced along with implemented solutions will be discussed in detail. Recent MLL sectioning results obtained by manual polishing, reactive ion etching, and focused ion-beam milling are promising. Multilayers composed of WSi2/Si, Vxsix/Si, Cr/Sc, V/B4C, and W/B4C benefit when grown with a small percentage of nitrogen. Reflective multilayer optics for a wide variety of applications, from ~200eV high energy-density experiments, to 80KeV synchrotron experiments will be presented. Two ion-beam sources (one RF and one DC) incorporating multiple gas mixing are being installed in the MLL deposition system over the next couple months which will expand our capabilities.
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