The orbital symmetries of electron-doped iron-arsenide superconductors Ba(Fe1-xCox)(2)As-2 have been measured with x-ray absorption spectroscopy. The data reveal signatures of Fe d electron itinerancy, weak electronic correlations, and a high degree of Fe-As hybridization related to the bonding topology of the Fe d(xz+yz) states, which are found to contribute substantially at the Fermi level. The energies and detailed orbital character of Fe and As derived unoccupied s and d states are found to be in remarkably good agreement with the predictions of standard density-functional theory.

C. Parks Cheney,1 F. Bondino,2 T. A. Callcott,1 P. Vilmercati,1 D. Ederer,3 E. Magnano,2 M. Malvestuto,4 F. Parmigiani,2,5 A. S. Sefat,6 M. A. McGuire,6 R. Jin,6 B. C. Sales,6 D. Mandrus,6 D. J. Singh,6 J. W. Freeland,7 and N. Mannella1,* 1Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA 2IOM CNR Laboratorio TASC, S.S. 14, km 163.5, I-34012 Trieste, Italy 3Department of Physics, Tulane University, New Orleans, Louisiana 70118, USA 4Sincrotrone Trieste S.C.p.A., Area Science Park, S.S. 14, km 163.5, I-34012 Trieste, Italy 5Dipartimento di Fisica, Università degli Studi di Trieste, I-34127 Trieste, Italy 6Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 7Advance Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA Received 16 September 2009; revised manuscript received 2 February 2010; published 18 March 2010

Purpose: Recently, a medical device (Arthro-BST™, Bio Syntech Canada Inc.) was developed to assess the electromechanical properties of articular cartilage during arthroscopy by measuring streaming potentials.The purpose of this study was to evaluate the reliability of this device and to correlate Arthro-BST™ measurements to biochemical, biomechanical and geometrical properties of human articular cartilage.Methods and Materials: Streaming potentials were mapped using the Arthro-BST™ in vitro at 102 positions on the articular surfaces of one human cadaver knee.Five different users performed 3 consecutive mappings on each surface.27 cartilage disks were isolated and collagen, mature (hydroxylysyl-pyridinoline) and immature (divalent keto-imine) collagen crosslinks.The reliability of the Arthro-BST measurements among different users was evaluated using the Results:The high value of the computed ICC (0.87) from streaming potentials demonstrated the important ability of the Arthro-BST to provide user independent cartilage electromechanical properties.moduli and cartilage thickness in a manner similar to a previous parameter correlated positively with the collagen content and the ratio of mature to immature crosslinks.Conclusions: Streaming potentials from the Arthro-BST™ provided a reliable indicator of composition and biomechanical properties of human articular cartilage.This instrument could be used to assess cartilage quality during clinical arthroscopic procedures.

This paper presents the status and the operation conditions of the 1.3 GeV storage ring at the Center for Advanced Microstructures and Devices (CAMD). An overview of existing beamlines with their relevant parameters is given and four beamlines that came into operation over the last two years are discussed in some detail.

Spectra for the manganese $3s\ensuremath{\rightarrow}2p$ x-ray emission after resonant and nonresonant photon excitation of a $2p$ electron are presented for metallic manganese, ${\mathrm{MnF}}_{2}$, $\mathrm{MnO}$, and ${\mathrm{LaMnO}}_{3}$. The absorption and emission spectra are compared with the results of free-ion calculations for ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Mn}}^{3+}$. The experimental absorption spectrum of ${\mathrm{MnF}}_{2}$ is in very good agreement with the calculation for ${\mathrm{Mn}}^{2+}$, while the absorption of the other compounds is found to be a superposition of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Mn}}^{3+}$. There are noticeable differences among the compounds, both in the relative positions and intensities of the emission peaks. The resonant emission spectra from ${\mathrm{MnF}}_{2}$ is dominated by decay from the $2{p}^{5}3{d}^{6}$ resonant configuration, while ``normal'' fluorescence is found to predominate in ${\mathrm{LaMnO}}_{3}$. In metallic manganese and $\mathrm{MnO}$ the emission spectra are well described as a superposition of these two extreme cases.

We present high-resolution x-ray fluorescence spectra, corrected for self-absorption, following resonant excitation of a Ti(2p(1/2)) electron in TiO2. Several transitions are studied that show complex behavior as a function of photon excitation energy, indicative of interaction in the excitation and decay channels. Three peaks are identified as transitions resulting from the excitation of a 2p(1/2) electron, one of them corresponding to direct valence emission with a 3d spectator electron and the other two to participator emission following the Coster-Kronig decay of the 2p(1/2) hole. Additional emission features at higher photon energies correspond to valence emission in the presence of a charge-transfer excitation that has been found in the 2p x-ray photoelectron spectroscopy spectrum, and also in the x-ray absorption spectrum. A detailed analysis of the energy dispersion versus excitation energy provides information about the dynamical processes involved. The results are interpreted in terms of the calculated band structure of the compound.

The electronic structure of the Mn-based dycyanamide molecular magnetic crystal has been investigated using theoretical density-functional-based methods and experimental spectra. All data are in accord with a small gap insulator with a lattice consisting of Mn+2(d(5)) ions that are antiferromagnetically coupled at low temperatures. Due to partial covalent bonding with neighboring atoms, the local moments of the Mn atoms are reduced by about 10% as compared to an isolated ion. Calculated exchange constants suggest a antiferromagnetic/ferromagnetic energy difference of 36 meV per unit cell. Inclusion of spin-orbit coupling allows for the determination of the magnetic anisotropy parameter and the preferred axis of magnetization. The results are in good agreement with previous experiments.

We present experimental evidence that the newly discovered multiatom resonant photoemission effect can be observed via secondary decay processes of the primary core hole: Auger electron emission, from Fe2O3, where the O KL23Lu23 intensity is enhanced by 90% when h v is tuned to the Fe L-3 edge, and fluorescent x-ray emission, from MnO, where the O K alpha fluorescence intensity shows an enhancement of more than 100% at the Mn L-3 edge when properly corrected for saturation and self-absorption effects.

Absolute inclusive and exclusive cross sections for ionization of H- and He by Compton scattering are presented and analyzed. The exclusive cross section for ionization of one electron, leaving the second electron in the ground state, is 20% smaller for H- than for He. Furthermore, the exclusive cross section for ionization with excitation to the first excited state is seven times larger for H- than for He. However, at high energies the inclusive Compton cross sections for both H- and He are within 1% of two times the Thomson cross section for elastic scattering of a free electron, even when ground-state correlation is accurately included. A general analysis based on quasielastic scattering is applied to both shake and correlated calculations.

The electronic structure of organic superconductors kappa-(ET)(2)Cu[N(CN)(2)]Br and kappa-(ET)(2)Cu(NCS)(2) has been studied in detail by means of soft x-ray fluorescence spectroscopy. Cu L-3, S L-2,L-3, C K alpha, and N K alpha x-ray emission spectra are measured near the corresponding thresholds with synchrotron radiation. The experimental information about site-selective and symmetry-restricted partial density of states in the valence band of both compounds is compared with first-principles band-structure calculations and ultraviolet photoemission spectral It is found that copper is monovalent in both compounds indicating that the electron is transferred from (ET) dimer to Cu(NCS)(2) and Cu[N(CN)(2)]Br and is localized mainly on the Cu site. [S0163-1829(99)03542-0].

Synchrotron base O 1s and N 1s photoabsorption spectroscopy have been used to determine the composition and thickness of oxynitride films grown in N2O on a Si(100) surface. Core-level photoabsorption spectroscopy is shown to be a very sensitive probe capable of measuring surface coverages lower than 0.1 monolayers of N (6.5×1013 N atoms/cm2). Film composiion was monitored as a function of growth to demonstrate the stoichiometry reversal from primarily N terminated surfaces in thin films to nearly pure SiO2 in films thicker than ∼ 20 Å. A sample with a 60 Å oxynitride film was depth-profiled by etching in HF and was shown, via N 1s absorption spectroscopy, to have N segregation within 10 Å above the Si/SiO2interface.

Soft-x-ray emission spectra for the La N4,5O2,3 transitions in lanthanum aluminate LaAlO3 include contributions from several relatively intense multiplet lines near 80 eV. The appearance of this spectrum contrasts sharply with the three diagram lines observed for the N4,5O2,3 emission spectrum of Ba in BaF2. An atomic model of the La N4,5O2,3 transition, assuming single occupancy of the 4f shell by a spectator electron, provides a good approximation of the measured spectrum. Emission features due to the low-energy P-3(0) and D-3(0) terms of the 4d(9)4f configuration are also apparent in the LaAlO3 emission spectra, but not in emission spectra from BaF2. Reflection measurements indicate that the 4f level is not occupied in the ground state in LaAlO3. The data suggest that charge transfer from ligand orbitals following creation of a 4d vacancy prior to the emission process is the predominant mechanism giving rise to the required 4f occupancy.

A determination of the alignment of He+(2p) between the n = 2 and 3 levels was carried out by measuring the angular distribution of the 304-angstrom fluorescence that follows photoionization with synchrotron radiation. The alignment A(c)0 is related to the cross-section ratio zeta = sigma-2pkd/sigma-2p and thus provides a means of separating the kd and ks partial-wave contributions to the 2p ion production. The partial-cross-section ratio R = sigma-2p/sigma-2s was also determined by measuring the fluorescence signal at the magic angle with and without an external electric field that quenches the 2s ions. With these data a partition of the n = 2 cross section into the partial cross sections sigma-2skp, sigma-2pks, and sigma-2pkd was carried out. The effect of the broad 1(3) autoionizing resonance in these partial cross sections was determined. A comparison with the results of a many-body-perturbation-theory calculation shows good agreement for the alignment, as well as for R, sigma-2skp, and sigma-2pks, but somewhat of a discrepancy for sigma-2pkd.

We present oxygen K soft x-ray emission spectra for the YBa/sub 2/Cu/sub 3/O/sub x/ compounds with x nominally equal to 6, 6.5, and 7 and compare them with x-ray emission spectra determined from recent band-structure calculations. The K emission spectrum of O provides a measure of the p-type local partial density of states to (p-LPDOS) at the oxygen sites. As x decreases from 7-delta about 6.5, a chemical shift of the entire spectrum to lower energy indicates that screening is modified for all oxygen sites. The integrated intensity of the spectra is nearly unchanged by oxygen removal, indicating an increase in p-LPDOS per oxygen site. These results and changes in the spectral shape suggest that itinerant electron density near the O atoms is reduced and bound electron density is increased as oxygen is removed.