X-ray dichroism

However Allen [641] and others have argued against an atomic interpretation. It is probably fair to say that atomic multiplet theory and the condensed matter models have not yet been completely reconciled. This question is important high temperature superconductors of the form RBa2Cu306, where R can be any member of the rare-earth series of elements except Ce and Pr, have attracted much attention. A fluctuation in valence involving 4/ electrons is likely to be involved in the emergence of high temperature superconductivity for these materials. 

Experimental data on the free atom provide an essential benchmark, without which interpretation of data for the solid must remain somewhat speculative. 

The most interesting case is photoemission of 4/ electrons in the rare earths as noted in the previous section, because of the collapsed nature of the 4/ orbitals, the photoemission spectrum can be interpreted completely even in the solid by atomic multiplet theory, and this applies also to magnetic circular dichroism. Thole and van der Laan [642] have derived sum rules for magnetic dichroism in rare-earth 4/ photoemission. They have shown that the integrated intensity is simply the sum over each sublevel of its occupation number times the total transition probability from that sublevel to the continuum shell. Polarisation effects in the 4/ photoemission spectra of rare earths are very large, and this tool based on quasiatomic analysis is of considerable significance it provides a new 

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H applied magnetic field MCXD magnetic circular X-ray dichroism... 

Mossbauer measurements, which are used to determine the local Fe moment and its direction at different temperatures for Tb/Fe, Dy/Fe and Nd/Fe, are presented in this section. Magnetic circular X-ray dichroism (MCXD) is a relatively new element-selective technique, which can be used to obtain information on magnetic properties for both R and T atoms one example of MCXD studies of Tb/Fe multilayers is given. 

Magnetic circular X-ray dichroism (MCXD) allows one to deduce direct information of local magnetic moments, anisotropy behavior, and characteristics of interface magnetism. 

Okamoto, S., Ishihara, S., and Maekawa, S. Theory of Raman scattering from orbital excitations in manganese oxides. Phys. Rev. B 2002, 66,014435-1-9. Templeton, D.H. and Templeton, L.K. X-ray dichroism and polarized anomalous scattering of the uranyl ion. Acta Crystallogr. A 1982, 38, 62—67. 

Materials characterization techniques, ie, atomic and molecular identification and analysis, ate discussed ia articles the tides of which, for the most part, are descriptive of the analytical method. For example, both iaftared (it) and near iaftared analysis (nira) are described ia Infrared and raman SPECTROSCOPY. Nucleai magaetic resoaance (nmr) and electron spia resonance (esr) are discussed ia Magnetic spin resonance. Ultraviolet (uv) and visible (vis), absorption and emission, as well as Raman spectroscopy, circular dichroism (cd), etc are discussed ia Spectroscopy (see also Chemiluminescence Electho-analytical techniques It unoassay Mass specthot thy Microscopy Microwave technology Plasma technology and X-ray technology). 

Results from an array of methods, including X-ray absorption, EXAFS, esr and magnetic circular dichroism, suggest that in all ureases the active sites are a pair of Ni" atoms. In at least one urease,these are 350 pm apart and are bridged by a carboxylate group. One nickel is attached to 2 N atoms with a fourth site probably used for binding to urea. The second nickel has a trigonal bipyramidal coordination sphere. 

MAGNETIC DICHROISM IN VALENCE BAND X-RAY PHOTO EMISSION SPECTROSCOPY... 

Ch. Brouder, and M. Hikam. Multiple scattering theory of magnetic x-ray circular dichroism. Phys. Rev. 

E. Dartyge, and A. Fontaine. K edge x-ray magnetic circular dichroism in molecular based magnets. Physica B 208 209 765 (1995). 

Small-angle X-ray scattering (SAXS), circular dichroism (CD), and UV spectroscopy at different temperatures were used to investigate the nature of calf-thymus DNA in aqueous solution, in the presence of [Me Sn] " (n = 1-3) species. The results demonstrate that the [MeSn(IV)] moiety does not influence the structure and conformation of the DNA double helix, and does not degrade DNA, as indicated by agarose gel electrophoresis. Inter alia, the radii of gyration, Rg, of the cross section of native calf-thymus DNA, determined by SAXS in aqueous solution in the presence of [Me Sn] " (n = 1-3) species are constant and independent of the nature and concentration of the [Me Sn] species. 

In this section we will discuss in some detail the application of X-ray diffraction and IR dichroism for the structure determination and identification of diverse LC phases. The general feature, revealed by X-ray diffraction (XRD), of all smectic phases is the set of sharp (OOn) Bragg peaks due to the periodicity of the layers [43]. The in-plane order is determined from the half-width of the inplane (hkO) peaks and varies from 2 to 3 intermolecular distances in smectics A and C to 6-30 intermolecular distances in the hexatic phase, which is characterized by six-fold symmetry in location of the in-plane diffuse maxima. The lamellar crystalline phases (smectics B, E, G, I) possess sharp in-plane diffraction peaks, indicating long-range periodicity within the layers. 

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