Materials Research with X-ray Micro-beams at the Advanced Photon Source

X-ray scattering has had a rich and prominent place in the history of materials research. For samples that are large single crystals, X-ray diffraction provides very detailed, high-quality information about the atomic structure of almost every kind. However, most engineering materials are not a large single crystal, but mixtures of materials or a poly-crystalline material. Still, X-ray diffraction using X-ray beams significantly larger than the structures being investigated has produced much excellent information. Examples of this are powder diffraction, texture analysis, strain analysis, etc. While these types of analyses have been very useful in providing a microscopic understanding, they do not provide the microscopic information that we really want. What we really want to have is this useful X-ray diffraction information for every volume element in our sample; not just the diffraction information about small volume elements, but all of the volume elements, exactly where they are in our sample, and how each one diffracts. This detailed spatial and structural information is what is needed for a full understanding of the source of the properties that we find in engineering materials.     

Resonant Inelastic X-ray Scattering: From band mapping to inter-orbital excitations

Resonant inelastic X-ray scattering (also known as resonant X-ray Raman spectroscopy when only valence and conduction states are involved in the final state excitation) has developed into a major tool for understanding the electronic properties of complex materials. Presently it provides access to electron excitations in the few hundred meV range with element and bulk selectivity. Recent progress in X-ray optics and synchrotron radiation engineering have opened up new perspectives for this powerful technique to improve resolving power and efficiency. We briefly present the basics of the method and illustrate its potential with examples chosen from the literature. To cite this article: J. Lüning, C.F. Hague, C. R. Physique 9 (2008).     

Advanced Photon Source

The Advanced Photon Source (APS) at Argonne National Laboratory is preparing for a major upgrade, centered on installation of a multibend achromat (MBA) lattice that will dramatically improve the brightness, coherence, and stability of the X-ray beams.     

Resonant inelastic X-ray scattering (RIXS) on magnetic EuCo2P2-based systems

The features of near-edge structure around the L ₃-Eu absorption edge are investigated in EuCo₂P₂, Pr_{1 ? x} Eu _x Co₂P₂ (x = 0.2, 0.4), and Nd_0.6Eu_0.4Co₂P₂ by means of resonant inelastic X-ray scattering (RIXS). Europium is shown to be in the intermediate valence state in all compounds. A comparison is made of the values of europium intermediate valence obtained by different methods employing the synchrotron radiation. The correlation between europium valence and the observed changes of magnetic ordering in the systems under investigation is discussed.     

Nuclear resonant scattering beamline at the Advanced Photon Source

The principal and engineering aspects of a dedicated synchrotron radiation beamline under construction at the Advanced Photon Source for nuclear resonant scattering purposes are explained. The expected performance in terms of isotopes to be studied, flux, and timing properties is discussed.This work is supported by the US-DOE-BES Materials Sciences, under Contract No. W-31-109-ENG-38.     

Lattice Dynamics and Inelastic Nuclear Resonant X-Ray Scattering

Measurement of thermal and elastic properties of materials, like phonon density of states, specific heat or speed of sound, by a new X-ray scattering technique is presented. Inelastic nuclear resonant scattering of X-rays produced from new electron storage rings, coupled with advances in high-energy-resolution crystal optics and fast detectors has enabled the development of a new method of analyzing the energy loss in a scattering process with a resolution of 10⁷ or better in the X-ray region of 6–30 keV. Some unique aspects like element (isotope) selectivity, the amount of material needed for analysis (nanograms) and physical size that X-rays can be focused (5 micrometer or better) favors this approach over more established techniques of neutron scattering, Mössbauer, and Raman spectroscopy. Applications to several unique cases (e.g., multilayers and high pressure) are discussed.     

软 X射线共振非弹性光散射及其应用

软 X射线共振非弹性光散射是近年来随着高亮度第三代同步辐射出现而发展起来的光散射光谱技术 ,可以用于对多原子构成的分子、凝聚态物质进行位置选择的价电子态结构的研究。与 X射线光电子能谱 ( XPS)或紫外光电子能谱 ( UPS)相比 ,这一光谱方法由于测量样品激发后产生的散射 X射线 ,因而不仅可以获得表面的原子分子信息 ,而且可以用于研究样品体内或掩埋薄层的原子分子。同时这一方法的共振特性使得其可以进行灵敏的元素选择测量。本文将介绍这一光散射光谱技术及其在原子分子物理、表面物理及凝聚态物理中的应用     

Resonant inelastic X-ray scattering (RIXS) spectroscopy at the Mn K absorption pre-edge—a direct probe of the 3d orbitals

A study of the Mn K absorption pre-edges in oxides using resonant inelastic X-ray scattering (RIXS) spectroscopy is presented. The energy transfer dimension enhances the separation of the pre-edge (predominantly 1s to 3d transitions) from the main K-edge and a detailed analysis is thus possible. The RIXS spectra are sensitive to the Mn spin state. The technique thus yields detailed information on the electronic structure that is not accessible in conventional K-edge absorption spectroscopy. The line splittings can be understood within a ligand field multiplet model, showing the importance of (2p,3d) two-electron interactions that give rise to the spin-sensitivity.     

Technical Reports: Time-Resolved Activities at the Advanced Photon Source Requiring the Pulsed Structure of the X-ray Beam

Scientific research in the time domain using the pulsed structure of the X-ray beams from a third-generation synchrotron source, such as the Advanced Photon Source (APS), has become a major interest among synchrotron users. The traditional material science, chemistry, and biology communities are getting an early glimpse of the potential impact of fast time-resolved X-ray studies. The scientific disciplines that have benefited from these studies include atomic and molecular physics, biology, chemical science, condensed matter physics, engineering science, environmental science, material science, and nuclear science. Technically, the turn-key-type femtosecond (fs) optical lasers with high peak power, used as pumps in many X-ray pump-probe experiments, have only recently become available.     

Bremsstrahlung Effect at Resonant Compton Scattering of a Photon by a Multielectron Atom

JETP Letters - The leading role of the bremsstrahlung at resonant Compton scattering of a hard X-ray photon by a multielectron atom has been theoretically predicted. This result can be important in...     

Development and Performance of Superconducting Undulators at the Advanced Photon Source

Several years ago, an article in SRN [1 Y. Ivanyushenkov and E. Moog, Synchrotron Radiation News, 24(3), 20–24 (2011).[Taylor &; Francis Online] , [Google Scholar]] with the same title as this article summarized the decade-long development of superconducting undulators (SCUs) at the Advanced Photon Source (APS). The article presented those developments leading to the point when the first prototype, called SCU0 and intended for installation at the APS, was under fabrication. SCU0 was built in 2012, its cryogenic performance has been extensively tested, and detailed magnet measurements of the device have been conducted. After verification that SCU0 met all of the technical requirements for APS insertion devices, it was installed in the APS storage ring in January 2013, commissioned in a record short time (two weeks), and became a routinely used source of hard X-rays at the APS Sector 6 ID beamline.     

Determination of Phonon Dispersion Curves at Gigapascal Pressures by Inelastic X-ray Scattering

The study of phonon dispersion curves of materials under hydrostatic pressure provides important information such as the evolution of sound velocities, elastic constants, interatomic potentials, phase transition mechanisms, etc. Until very recently, coherent inelastic neutron scattering was the only spectroscopic technique, which allowed performing these types of studies up to typically 10 GPa. Today, inelastic X-ray scattering with meV energy resolution provides a complementary spectroscopic technique, where, using diamond anvil cell techniques, pressures beyond 100 GPa can be reached.