Experimental determination of electric-field-induced differences in structure-factor phases of the order of 2%

Stahn, J.; Pucher, A.; Pietsch, U.; Zellner, J.; Weckert, E.

doi:10.1107/s0108767399009782

Cited by 28 publications

(1 citation statement)

References 10 publications

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“…The sample was a crystal of GaAs oriented to the (222) reflection. This reflection is very weak [63][64][65] because its structure factor is given by the difference of the atom form factors for Ga and As, which, far from absorption edges, corresponds to two electrons. The photon energy used for the experiment was 11.8655 keV, which is a few eV below the As K absorption edge.…”

Section: A Test Experimentsmentioning

confidence: 98%

Coherence conversion for optimized resolution in optical measurements – example of femtosecond time resolution using the transverse coherence of 100-picosecond X-rays

Adams

2015

Journal of Modern Optics

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A way is proposed to obtain a femtosecond time resolution over a picosecond range in laser-pump, X-ray probe spectroscopic measurements where the light source and the detector are much slower than that. It is based on a phase-space transformation from the time/bandwidth to the spatial/wavenumber domain to match the coherence properties of synchrotron radiation to the requirements of femtosecond experiments. In a first step, the geometry of the laser incidence maps time, t, of laser-induced femtosecond dynamics to a spatial coordinate, x. Then, a far-field X-ray diffraction pattern, i.e. the optical Fourier transform, is obtained from the laser-induced modifications of the sample properties, including shifts of X-ray absorption edges and changes in crystallographic unit-cell form factors. Whereas the first step is similar to previously used schemes for femtosecond time resolution, the second one is substantially different with specific advantages discussed in the text. Key to this technique is that the modulus of the Fourier transform is invariant with respect to translations ξ along x, which are due to the t − x correlation. It can, therefore, be acquired in a simple intensity measurement with a slow detector. The phase, which does vary strongly with ξ , is missing in the intensity data, but can be recovered through a heterodyning technique. Data from a demonstration experiment are presented. The same concept can be used to obtain attosecond time resolution with an X-ray free-electron laser.

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Section: A Test Experimentsmentioning

confidence: 98%

Coherence conversion for optimized resolution in optical measurements – example of femtosecond time resolution using the transverse coherence of 100-picosecond X-rays

Adams

2015

Journal of Modern Optics

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New Conformations and Binding Modes in Halogen-Bonded and Ionic Complexes of 2,3,5,6-Tetra(2‘-pyridyl)pyrazine

Padgett

Walsh

Drake

et al. 2004

Crystal Growth & Design

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The enormous potential of 2,3,5,6-tetra(2‘-pyridyl)pyrazine (tppz) as a versatile multisite component for the design and construction of complex structures is demonstrated by the preparation of several new complexes that possess previously unobserved binding modes and conformations. tppz forms halogen-bonded complexes with diiodine and organoiodides and forms ionic compounds in which tppz is either di- or tetraprotonated. We have prepared two new halogen-bonded complexes of tppz with diiodine and with tetraiodoethylene (TIE). Both possess extended chain structures of alternating donors and acceptors, with the tppz donors in the diiodine complex linked by two neutral -I2·I2·I2- chains. Two new polyiodide complexes of tppz have also been prepared, one of which has di- and the other tetraprotonated cations. A bromide salt of the tetraprotonated tppz cation has also been prepared and found to be isomorphous with the known chloride salt. In the diiodine complex, tppz·6I2, the conformation of tppz is similar to that found in the metastable, tetragonal polymorph of the free donor, and obeying Ostwald's rule of stages, decomposes through solid-state loss of I2 to give exclusively this polymorph. In the TIE complex, tppz·TIE, has a previously unreported conformation, but decomposes to the thermodynamically stable monoclinic polymorph upon loss of TIE. The diprotonated cation, [tppz(H)2]2+, which forms two intramolecular N−H···N hydrogen bonds and crystallizes with (I2·I3)- anions, has a twisted conformation as opposed to the bowed conformation found for this cation with tetraphenylborate counterions. Tetraprotonated tppz hydrogen bonds to two iodide anions to form [tppz(H2I)2]2+ cations, similar to the bromide and chloride salts, but with triiodide anions rather than hydrated halides as in the lighter derivatives.

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Dynamical Theory of X-Ray Diffraction

Authier

2003

394

658

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X-ray diffraction is a major tool for the study of crystal structures and the characterization of crystal perfection. Since the discovery of X-ray diffraction by von Laue, Friedrich, and Knipping in 1912 two basic theories have been used to describe this diffraction. One is the approximate geometrical, or kinematical theory, applicable to small or highly imperfect crystals; it is used for the determination of crystal structures and the study of powders and polycrystalline materials. The other one is the rigorous dynamical theory, applicable to perfect or nearly perfect crystals and, for that reason, is the one used for the assessment of the structural properties of high technology materials. It has witnessed exciting developments since the advent of synchrotron radiation. This book provides an account of the dynamical theory of diffraction and of its applications. The first part serves as an introduction to the subject, presenting early developments, Ewald's theory of dispersion and the basic results of Laue's dynamical theory. This is followed in the second part by a detailed development of the diffraction and propagation properties of X-rays in perfect crystals, including the study of anomalous absorption, Pendellösung, grazing incidence diffraction (GID) and n-beam or multiple-beam diffraction. The third part constitutes an extension of the theory to the case of slightly and highly deformed crystals. The last part gives three applications of the theory: X-ray optics for synchrotron radiation, location of atoms at surfaces and interfaces and X-ray diffraction topography.

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Experimental determination of electric-field-induced differences in structure-factor phases of the order of 2%

Cited by 28 publications

References 10 publications

Coherence conversion for optimized resolution in optical measurements – example of femtosecond time resolution using the transverse coherence of 100-picosecond X-rays

Coherence conversion for optimized resolution in optical measurements – example of femtosecond time resolution using the transverse coherence of 100-picosecond X-rays

New Conformations and Binding Modes in Halogen-Bonded and Ionic Complexes of 2,3,5,6-Tetra(2‘-pyridyl)pyrazine

Dynamical Theory of X-Ray Diffraction

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