X-ray fluorescence spectra of metals excited below threshold

X-ray scattering spectra of Cu and Ni metals have been measured using monochromatic synchrotron radiation tuned from far above to more than 10 eV below threshold. Energy conservation in the scattering process is found to be sufficient to explain the modulation of the spectral shape, neglecting momentum conservation and channel interference. At excitation energies close to and above threshold, the emission spectra map the occupied local partial density of states. For the sub-threshold excitations, the high-energy flank of the inelastic scattering exhibits a Raman-type linear dispersion, and an asymmetric low energy tail develops. For excitation far below threshold the emission spectra are proportional to a convolution of the occupied and unoccuppied local partial densities of states.Comment: 10 pages, 3 figures, http://link.aps.org/doi/10.1103/PhysRevB.68.04511

State dependent fluorescence yields through the core valence Coulomb exchange parameter

Total and partial fluorescence yield PFY L edge x ray absorption spectra differ from the transmission x ray absorption spectra XAS through state dependent fluorescence yield across the XAS. For 3d1 to 3d9 in octahedral symmetry we apply simulations of PFY and XAS and show how the atomic 2p3d Coulomb exchange parameter Gpd governs the differences in the L3 L2 L3 branching ratio between PFY and XAS. Gpd orders the XAS final states following Hund s rules creating a strong state dependent fluorescence decay strength variation across the XAS leading to the differences between PFY and XA

Synsedimentäre Deformationen im Unterern Muschelkalk des Germanischen Beckens

In weiten Bereichen des Germanischen Beckens kennzeichnen Deformationsstrukturen, deren Genese bisher nur unzureichend geklärt war, die marinen Ablagerungen des Unteren Muschelkalks. Ergebnisse feinstratigraphischer Profilaufnahmen, Dokumentationen der Strukturen im Aufschlußbereich sowie Dünnschliff- und rasterelektronenmikroskopische Untersuchungen ermöglichten Aussagen über die Klassifikation und die Entstehung dieser Strukturen. In Abhängigkeit von der faziellen Ausbildung der Karbonate dominieren in-situ entstandene Deformationsstrukturen bzw. gravitativ umgelagerte Sedimenteinheiten (Rutschungsablagerungen) das strukturelle Inventar. Die Untersuchungsergebnisse lassen auf erhöhte Porenfluiddrücke infolge seismischer Erschütterungen als Auslöser für die Rutschungen schließen. Hinweise auf die tektonische Aktivität am Nordrand der Tethys während der Zeit des Anis stellen auch die in den Ablagerungen der Wellenkalk-Fazies weitverbreiteten Sigmoidalklüftungs-Strukturen dar, deren Entstehung auf Erdbebenerschütterungen zurückgeführt werden konnte. Die Darstellung und Interpretation ihrer über große Entfernungen konstanten Orientierungsrichtungen ermöglichten die Lokalisierung der Epizentren in der Umgebung der Moravo-Silesischen- sowie der Burgundischen Pforte

Calibration for the ATLAS Level-1 Calorimeter Trigger

This thesis describes developments and tests that are necessary to operate the Pre-Processor of the ATLAS Level-1 Calorimeter Trigger for data acquisition. The major tasks of Pre-Processor comprise the digitizing, time-alignment and the calibration of signals that come from the ATLAS calorimeter. Dedicated hardware has been developed that must be configured in order to fulfill these tasks. Software has been developed that implements the register-model of the Pre-Processor Modules and allows to set up the Pre-Processor. In order to configure the Pre-Processor in the context of an ATLAS run, user-settings and the results of calibration measurements are used to derive adequate settings for registers of the Pre-Processor. The procedures that allow to perform the required measurements and store the results into a database are demonstrated. Furthermore, tests that go along with the ATLAS installation are presented and results are shown

Crystal-field splitting in coadsorbate systems: c (2x2) CO/K/Ni (100)

It is demonstrated how the crystal field splitting (CFS) fine structure can be used to characterize a coadsor-bate system. We have applied K 2p x-ray absorption spectroscopy (XAS) to the c(2x2) CO/K/Ni(100) system. The CFS fine structure is shown to be sensitive to the the local atomic environment, the level of interaction, and the chemical state of the alkali atoms. From angle dependent XAS measurements, combined with x-ray photoelectron spectroscopy, a significant K-CO electrostatic adsorbate-adsorbate interaction is found, whereas the K-Ni interaction is substantially weaker. The present results provide evidence for a coad-sorbed overlayer best described in terms of the properties associated with an ionic (two-dimensional) crystal

Laser pump X ray probe experiments with electrons ejected from a Cu 111 target space charge acceleration

A comprehensive investigation of the emission characteristics for electrons induced by X rays of a few hundred eV at grazing incidence angles on an atomically clean Cu 111 sample during laser excitation is presented. Electron energy spectra due to intense infrared laser irradiation are investigated at the BESSY II slicing facility. Furthermore, the influence of the corresponding high degree of target excitation high peak current of photoemission on the properties of Auger and photoelectrons liberated by a probe X ray beam is investigated in time resolved pump and probe measurements. Strong electron energy shifts have been found and assigned to space charge acceleration. The variation of the shift with laser power and electron energy is investigated and discussed on the basis of experimental as well as new theoretical result

Classification Of Flow-Based Assembly Structures For The Planning Of Flexible Mixed-Model Assembly

The increasing product variance due to the growing individualization of customer requirements leads to smaller batch sizes and higher process time spreads in mixed-model assembly. The resulting decline in efficiency pushes conventional, less flexible assembly lines to the limits of their economic viability. Matrix assembly is an approach to increase flexibility and efficiency by decoupling workstations and dissolving cycle time constraints while maintaining flow. Both matrix and line assembly are flow-based assembly structures characterized by assembly objects moving according to the flow principle. Due to the numerous design options of flow-based assembly structures and the need to consider flexibility as a central decision criterion, the complexity of structural planning increases. The variety of the design options as well as their compatibility make it challenging for assembly planners to decide which configuration provides sufficient flexibility for their use case. This paper presents a novel level-based classification for flow-based assembly structures that identifies the relevant configurations, ranks them according to provided flexibility, and breaks down the characteristics as well as their compatibility. The classification enables planners to efficiently compile, evaluate and select the flow-based structure configurations suitable for the individual use case during assembly structure planning. Planning efficiency and results are improved by transparently providing all configurations and their characteristics' compatibility to the planner without any research effort. The configuration selection focusing on flexibility by means of the classification can be the starting point of a subsequent simulation of the system behavior concerning efficiency

Flexibility-Driven Planning Of Flow-Based Mixed-Model Assembly Structures

Trends such as mass customization, changing customer preferences and resulting output fluctuations increasingly challenge the production industry. Mixed-model assembly lines are affected by the rising product variety, which ultimately leads to ascending cycle time spreads and efficiency losses. Matrix assembly addresses these challenges by decoupling workstations and dissolving cycle time constraints while maintaining the flow. Both matrix and line assembly are flow-based assembly structures characterized by assembly objects moving along the stations. In assembly system planning, competing assembly structures are developed and the one best meeting the use case's requirements is selected for realization. During assessing requirements and selecting the superior assembly structure, the systematic consideration of flexibility is often not ensured within the planning approach. Therefore, a preferred assembly structure may not have the flexibility required for a use case. The systematic and data-driven assessment of required and provided flexibility in assembly system planning is necessary. This paper presents an assessment model that matches a use case's requirements with the flexibility of flow-based assembly structures based on production program and process data. On the one hand, requirements are defined by flexibility criteria that evaluate representative product mixes and process time heterogeneity. On the other hand, provided flexibility of flow-based assembly structures is assessed in a level-based classification. A method for comparing the requirements and the classification's levels to prioritize assembly structures for application in a case is developed. The flexibility requirements and assembly structure of an exemplary use case are determined and discussed under the planning project's insights to evaluate the developed model. This work contributes to the objective and data-driven selection of assembly structures by utilizing use case-specific data available during the phase of structural planning to meet flexibility requirements and ensure their consideration along the assembly planning process

Ultrafast electronic processes in an insulator The Be and O sites in BeO

The short time dynamics of amorphous beryllium oxide a BeO has been investigated for electronic excitation ionization by fast incident electrons, as well as by Ar7 , Ar15 , Xe15 , and Xe31 ions at velocities of 6 10 the speed of light. Site specific Auger electron spectra induced by fast heavy ions are the central point of this investigation. Electron induced Auger spectra serve as a reference and electron energy loss EELS spectroscopy as well as resonant inelastic X ray scattering RIXS are invoked for quantitative understanding. For the heavy ion case, we observe strong variations in the corresponding spectral distributions of Be K and O K Auger lines. These are related to local changes of the electron density, of the electron temperature and even of the electronic band structure of BeO on a femtosecond time scale after the passage of highly charged heavy ions

Time and Angle Resolved Time of Flight Electron Spectroscopy for Functional Materials Science

Electron spectroscopy with the unprecedented transmission of angle resolved time of flight detection, in combination with pulsed X ray sources, brings new impetus to functional materials science. We showcase recent developments towards chemical sensitivity from electron spectroscopy for chemical analysis and structural information from photoelectron diffraction using the phase transition properties of 1T TaS2. Our development platform is the SurfaceDynamics instrument located at the Femtoslicing facility at BESSY II, where femtosecond and picosecond X ray pulses can be generated and extracted. The scientific potential is put into perspective to the current rapidly developing pulsed X ray source capabilities from Lasers and Free Electron Laser