X-edge spectra

X-edge spectra of cobalt compounds appear quite similar to those of manganese compounds. The ionic cobaltous salts and hydrates produce t3q>e I spectra. In Fig. 9 and 10 the spectra of the salts (except for CoBrj) have their principal maximum at 18-20 ev. Spectra of the cobaltic salts stabilized with a coordination sphere of ammonia or of ethylene diamine, shown in Figs. 11 and 12, are all very similar, are of typo I, and have their... 

Early work on pure metals, solid-solution alloys, and intermetallic compounds has been reviewed by Azaroff and Pease (9). Some of the very best X-ray absorption X-edge spectra for 3d transition metals were reported in 1939 by Beeman and Friedman (24), who applied band theory for their interpretation. Up to the early 1960s X-ray band spectra of metals were mainly explained in terms of a density of states multiplied by a transition probability. 

Finally, Figure 25 shows the experimental Fe X-edge spectra of two trioctahedral... 

Mansour, A. N., Cook, J. W., and Sayers, D. E., "Quantitative Technique for Determination of the Number of Unoccupied d Electron States In a Pt Catalyst from the L X-ray Absorption Edge Spectra," J. Chem. Phys. (to be published). 

Figure 27. In situ X-ray absorption spectra around the ruthenium X-edge for an electrode modified with (A) one and (B) five monolayers of [Ru(v-bpy)3]2+. (C) Spectrum of bulk [Ru(bpy)3]2+.

Another example of the potential utility of polarized edge spectra for structure determination is found for [MoO J2" (28). This molecule has C2V symmetry and the C2 axes of all of the molecules in the unit cell are collinear. Thus, when the crystal is oriented with the polarization parallel to the S-S interatomic vector, the polarization is perpendicular to the Mo-0 bonds and nearly parallel to the Mo-S bonds. Similarly, the crystal can be oriented with the polarization perpendicular to the Mo-S bonds and nearly parallel to the Mo-0 bonds. For both orientations, excellent agreement was obtained with SCF-X a calculations of the edge structure (j ). 

The Fe K-edge spectra were recorded in the transmission mode and a metallic iron foil spectrum was measured simultaneously with each sample spectrum for energy calibration. X-ray absorption spectra for each sample were collected from 7,520 to 8,470 eV, with a step size of 0.40 eV and acquisition times of ca. 68 s per sample. Measuring each sample, in turn, and repeating... 

The problems associated with quantitative studies of structure based upon this viewpoint of X ray absorption-edge spectra may be similar to those encountered using electron beams of comparable energy, 3 to 100 ev., to carry out electron diffraction studies of crystal structure. Qualitatively, this analogy can be carried further, as both the X ray spectra and the electron beam diffraction in this energy range are influenced by only the first few atom layers. 

Fio. 1. Four distinct types of X-ray absorption edge spectra of manganese in varying chemical states. 

It should be noted that there has been some confusion In the literature with respect to the apparent oxidation state of the T3 site In different T2D laccase preps. This derives from the use of Indirect methods to define oxidation state. We have run x-ray edge spectra of T2D laccase prepared by four of the research groups strongly Involved In this field, and In all cases the Type 3 site Is found to be fully reduced. 

Conradson, S. D Abney, K. D. et al. 2004. Higher order speciation effects on plutonium L3 X-ray absorption near edge spectra. Inorganic Chemistry, 43, 116-131. 

Fig. 19. Combined QEXAFS and temperature-programmed sulfiding results of a Mo/ A1203 catalyst during sulfiding in a H2S/Ar gas mixture (a) Fourier transforms of the in situ EXAFS spectra above the Mo X-edge (b) variation in the H2S concentration in the gas outlet from the in situ EXAFS cell as simultaneously recorded by a mass spectrometer (61).

The mixed oxides obtained by hydrolysis at neutral pH of TIOT and TEOS over a wide range of compositions have also been investigated. The X-ray absorption near-edge spectra (XANES) of the mixed oxides having a composition corresponding to Ti Si = 1 8 (Fig. 4) indicate that Tiiv is present not in an octahedral coordination, as in anatase, but instead in a lower coordination, 5- or a mixture of 4-, 5-, and 6-coordination. 

Figure 2 Comparison of AVBbuik, AVBC]asttT, and the AVB K1(iei, where AVBI11D(iei was obtained using eq. 1 with an optimal AU value of 3.1 eV. Here AVB U1 kand AVBduster have been area normalized. Insert Illustration of the spin-orbital coupling effects in the X-ray absorption L2)3 edge spectra and 5d valence band.

Objections against these findings were soon raised. The strongest peak attributed to element 126 could experimentally be accounted for [55] by a prompt y-ray from the (p,n) nuclear reaction with natural 140Ce, a major component of the monazite crystals. The weaker peaks were shown to stem from to K x-rays from traces of ordinary elements such as antimony and tellurium [56]. When a more specific technique for the excitation of x-ray spectra was applied to the inclusions, namely by monochromatic synchrotron radiation tuned to the x-ray absorption edges, the evidence for superheavy elements vanished [57,58]. Furthermore, attempts failed [59] to detect them in bulk monazites through isolation of an A>294 fraction with a mass... 

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