Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session N6: Condensed Matter Physics at Synchrotron Facilities: History as Prologue to the Future |
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Sponsoring Units: FHP DPB Chair: David Moncton, Massachusetts Institute of Technology Room: Colorado Convention Center 207 |
Wednesday, March 7, 2007 8:00AM - 8:36AM |
N6.00001: Soft X-Ray Science -- From Photon Drought to X-Ray Lasers Invited Speaker: Soft x-ray science, loosely defined as research with 200-2000 eV photons, has come a long way over the last 30 years. This talk highlights some of the scientific developments and gives a glimpse of the future. Today, high-intensity soft x-rays are available with meV spectral resolution, picosecond pulse lengths and nanoscale spot sizes. Their tunable energy and polarization allows the control of electronic core-to-valence transitions that provide access to the fundamental charge and spin properties of valence electrons in matter. Large resonant cross sections associated with absorption edge resonances provide sensitivity to small numbers of atoms, as encountered in nanostructures, ultra-thin films, interfacial layers and surfaces. Presently, the most advanced experiments use sophisticated spectro-microscopy and lensless coherent imaging techniques with nanoscale spatial and picosecond temporal resolution. On the horizon are experiments with soft x-ray lasers which, among other things, will provide femtosecond snapshots of matter. [Preview Abstract] |
Wednesday, March 7, 2007 8:36AM - 9:12AM |
N6.00002: Inelastic X-ray Scattering Invited Speaker: This presentation is devoted to review the Inelastic X-ray Scattering (IXS) method to study atomic density fluctuations. The IXS as a complement to neutrons has been suggested for many years now with a first attempt dating back to the eighties. Only the advent of Hard X-ray third generation synchrotron light sources has allowed the establishment of IXS as a powerful routine technique for condensed matter studies. It has enabled important breakthroughs in our understanding of phonon-like excitations in disordered materials and matter at extreme conditions. The very small gauge volume and possible future advances in instrumentation allow to expect further developments in phonon microscopy. [Preview Abstract] |
Wednesday, March 7, 2007 9:12AM - 9:48AM |
N6.00003: Surface Structure as a Foundation of Nanotechnology Invited Speaker: The three generations of synchrotron sources achieved to date, parasitic, dedicated and undulator-based, have each time revolutionized the field of X-ray diffraction. Surface structure determination, demonstrated (but very difficult) already with Coolidge tube sources, benefited from the enormous flux gain in the first generation, such as SSRL. Dedicated 2nd-generation sources, such as NSLS, allowed in-situ surface preparation and reliable steady beams to be available when a surface was ready to measure. Third generation sources, such as APS, enormously improved the brightness, hence coherence, and thus allowed access to the surfaces of nanoparticles. This talk will illustrate how these technological advances led to two significant scientific breakthroughs. The concept of crystal truncation rods (CTR) led to new views of how the surface is a modification of, but still an extension of the bulk crystal structure. The development of lensless coherent x-ray diffraction (CXD) imaging has allowed access to the structure of nanocrystalline materials by three-dimensional phase mapping of the particle interiors. The structural principles of these new nano materials are being investigated at present using these new methods. [Preview Abstract] |
Wednesday, March 7, 2007 9:48AM - 10:24AM |
N6.00004: Magnetic X-Ray Scattering Invited Speaker: The 1980s saw the convergence of the development of synchrotron sources; the development of techniques to grow new materials layer by layer, and the realization that x-rays could probe the magnetic properties of materials. In addition to magnetic x-ray scattering, most magneto-optical effects have been extended from the visible to the soft x-ray region. Because of the tunability of both the energy and the polarization, synchrotron sources are element and site specific probes, and there are large resonant enhancements in the scattering or absorption cross sections at atomic absorption edges. Synchrotron radiation is routinely used to study the magnetic polarization of different components of a material and to separate their spin and orbital angular momentum densities. In addition synchrotron radiation can be used to determine the interplay between the atomic, orbital and magnetic ordering in materials. The history and current trends in magnetic x-ray scattering will be reviewed. Future trends include further development of the spectroscopic aspects of magnetic scattering and probing magnetism on smaller and smaller length scales and at shorter and shorter time scales. [Preview Abstract] |
Wednesday, March 7, 2007 10:24AM - 11:00AM |
N6.00005: The Use of Coherent X-Ray Beams to Study the Dynamics of Soft Condensed Matter Systems Invited Speaker: The study of slow dynamics in soft condensed matter systems has been of interest for many years. One of the most powerful techniques for studying dynamics at these time scales has been Dynamical Light Scattering (DLS). However, it was recognized over twenty years ago that a similar application of X-rays in order to achieve shorter length scales and avoid problems of multiple and stray particle scattering, could open up whole new areas of research. The advent of the high-brilliance third generation synchrotron X-ray sources over a decade ago made it possible for the first time to deliver an intense beam of highly coherent X-rays, enabling many new applications of X-ray scattering, some of which will be discussed. In particular, the technique of X-ray Photon Correlation Spectroscopy (XPCS), the X-ray analog of DLS, has now become an exciting new research area with applications primarily in soft condensed matter. In this talk, we shall trace the development of the use of coherent X-ray beams from the early demonstrations at the NSLS, ESRF and APS synchrotron light sources to current applications which include the study of dynamical fluctuations in colloids and polymers and in particular the study of surface fluctuations in liquid films and membranes. We shall show how XPCS has yielded interesting new results on these systems difficult if not impossible to obtain by other techniques. \newline \newline I wish to acknowledge collaborations with Hyunjung Kim, Larry Lurio, Zhang Jiang, Christian Gutt, Metin Tolan, Tuana Ghaderi, Jyotsana Lal, Simon Mochrie, Miriam Rafailovich, Jonathan Sokolov, Chinhua Li, Tadanori Koga, Xuesong Jiao, Suresh Narayanan. [Preview Abstract] |
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