[en] Synchrotron Radiation (SR) has been widely used since the 80's as a tool for many applications of UV, soft X rays and hard X rays in condensed matter physics, chemistry and biology. The evolution of SR sources towards higher brightness has led to the design of low-emittance electron storage rings (emittance is the product of beam size and divergence), and the development of special source magnetic structures, as undulators. This means that more and more photons are available on a narrow bandwidth and on a small collimated beam; in other words there is the possibility of getting a high power in a coherent beam. In most applications, a monochromator is used, and the temporal coherence of the light is given by the monochromator bandwidth. With smaller and smaller sources, even without the use of collimators, the spatial coherence of the light has become appreciable, first in the UV and soft X ray range, and then also with hard X rays. This has made possible new or improved experiments in interferometry, microscopy, holography, correlation spectroscopy, etc. In view of these recent possibilities and applications, it is useful to review some basic concepts about spatial coherence of SR, and its measurement and applications. In particular we show how the spatial coherence properties of the radiation in the far field can be calculated with simple operations from the single-electron amplitude and the electron beam angular and position spreads. The gaussian approximation will be studied in detail for a discussion of the properties of the far field mutual coherence and the estimate of the coherence widths, and the comparison with the VanCittert-Zernike limit

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[en] This paper compares different approaches, reported in the literature, for obtaining thermodynamic statistical information from ESR and NMR measurements on the conformations of lipid bilayers. A statistical approach recently proposed by the authors has been employed to reexamine several literature values of order parameters and to calculate Helmholtz free energy and entropy. This approach was applied to egg-phosphatidycholine, cerebroside and gangliosoyds, spin labelled at different acyl chain positions, and to bilayered membranes containing phosphatidylcholine and different gangliosides (GM1, GD1a and GD1b) at increasing glycolipid mole percent. The variation of the stability of the membrane with the peroxidation is also reexamined at different intermembrane locations by various probes

[en] In the last decade holographic methods using hard X-rays were developed. They are able to resolve atomic distances, and can give the 3D arrangement of atoms around a selected element. Therefore, hard X-ray holography has potential applications in chemistry, biology and physics. In this article we give a general description of these methods and discuss the developments in the experimental technique. The capabilities of hard X-ray holography are demonstrated by examples

[en] We consider the theory and data analysis in Fourier-transform X-ray holography. We also report studies and experimental investigations of practical ways to generate a suitable holographic reference wave

[en] A comparison of electron beam size diagnostic in a storage ring by coherence measurement and imaging of Synchrotron radiation is made. Several experiments are reviewed: imaging by hard X-ray refractive lenses, interferometry by fresnel mirrors, Gabor holography of a fiber

[en] In coherent X-ray diffraction microscopy the diffraction pattern generated by a sample illuminated with coherent x-rays is recorded, and a computer algorithm recovers the unmeasured phases to synthesize an image. By avoiding the use of a lens the resolution is limited, in principle, only by the largest scattering angles recorded. However, the imaging task is shifted from the experiment to the computer, and the algorithm's ability to recover meaningful images in the presence of noise and limited prior knowledge may produce aberrations in the reconstructed image. We analyze the low order aberrations produced by our phase retrieval algorithms. We present two methods to improve the accuracy and stability of reconstructions

[en] The structural and magnetic properties of Fe_0.5Pd_0.5 alloys have been correlated using X-ray diffraction (XD), vibrating sample magnetometry (VSM) and transverse X-ray magnetic circular dichroism (TXMCD) at the Pd L_2,3 edges. XD indicates that codeposition of Fe and Pd, at elevated temperatures (350 deg. C), results in a well-ordered L1₀ phase which exhibits perpendicular magnetic anisotropy (PMA). On the other hand, codeposition at room temperature results in a disordered phase with in-plane easy-axis of magnetization. By codepositing at intermediate temperatures, a series of alloys has been produced with varying degree of compositional order. The TXMCD results show that increased compositional ordering leads to an increased orbital moment anisotropy favouring PMA. The magnetocrystalline anisotropy energy resulting from the orbital anisotropy is compared to VSM results

[en] Coherent X-ray diffraction microscopy is a method of imaging non-periodic isolated objects at resolutions only limited, in principle, by the largest scattering angles recorded. We demonstrate X-ray diffraction imaging with high resolution in all three dimensions, as determined by a quantitative analysis of the reconstructed volume images. These images are retrieved from the 3D diffraction data using no a priori knowledge about the shape or composition of the object, which has never before been demonstrated on a non-periodic object. We also construct 2D images of thick objects with infinite depth of focus (without loss of transverse spatial resolution). These methods can be used to image biological and materials science samples at high resolution using X-ray undulator radiation, and establishes the techniques to be used in atomic-resolution ultrafast imaging at X-ray free-electron laser sources

[en] We have studied the temperature-dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La_1-xSr_xMnO₃ (x= 0.3-0.4) with core and valence level photoemission (PE), x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS), extended x-ray absorption fine structure (EXAFS) spectroscopy and magnetometry. As the temperature is varied across the Curie temperature T_c, our PE experiments reveal a dramatic change of the electronic structure involving an increase in the Mn spin moment from ∼ 3 (micro)B to ∼ 4 (micro)B, and a modification of the local chemical environment of the other constituent atoms indicative of electron localization on the Mn atom. These effects are reversible and exhibit a slow-timescale ∼200 K-wide hysteresis centered at T_c. Based upon the probing depths accessed in our PE measurements, these effects seem to survive for at least 35-50 (angstrom) inward from the surface, while other consistent signatures for this modification of the electronic structure are revealed by more bulk sensitive spectroscopies like XAS and XES/RIXS. We interpret these effects as spectroscopic fingerprints for polaron formation, consistent with the presence of local Jahn-Teller distortions of the MnO₆ octahedra around the Mn atom, as revealed by the EXAFS data. Magnetic susceptibility measurements in addition show typical signatures of ferro-magnetic clusters formation well above the Curie temperature