K -shell diagram and hypersatellite spectra of 4d transition elements

The K-shell diagram (K alpha(1,2) and K beta(1,3)) and hypersatellite (HS) (K-h alpha(1,2)) spectra of Y, Zr, Mo, and Pd have been measured with high energy-resolution using photoexcitation by 90 keV synchrotron radiation. Comparison of the measured and ab initio calculated HS spectra demonstrates the importance of quantum electrodynamical (QED) effects for the HS spectra. Phenomenological fits of the measured spectra by Voigt functions yield accurate values for the shift of the HS from the diagram lines, the splitting of the HS lines, and their intensity ratio. Good agreement with theory was found for all quantities except for the intensity ratio, which is dominated by the intermediacy of the coupling of the angular momenta. The observed deviations imply that our current understanding of the variation of the coupling scheme from LS to jj across the periodic table may require some revision.The K-shell diagram (K alpha(1,2) and K beta(1,3)) and hypersatellite (HS) (K-h alpha(1,2)) spectra of Y, Zr, Mo, and Pd have been measured with high energy-resolution using photoexcitation by 90 keV synchrotron radiation. Comparison of the measured and ab initio calculated HS spectra demonstrates the importance of quantum electrodynamical (QED) effects for the HS spectra. Phenomenological fits of the measured spectra by Voigt functions yield accurate values for the shift of the HS from the diagram lines, the splitting of the HS lines, and their intensity ratio. Good agreement with theory was found for all quantities except for the intensity ratio, which is dominated by the intermediacy of the coupling of the angular momenta. The observed deviations imply that our current understanding of the variation of the coupling scheme from LS to jj across the periodic table may require some revision.The K-shell diagram (K alpha(1,2) and K beta(1,3)) and hypersatellite (HS) (K-h alpha(1,2)) spectra of Y, Zr, Mo, and Pd have been measured with high energy-resolution using photoexcitation by 90 keV synchrotron radiation. Comparison of the measured and ab initio calculated HS spectra demonstrates the importance of quantum electrodynamical (QED) effects for the HS spectra. Phenomenological fits of the measured spectra by Voigt functions yield accurate values for the shift of the HS from the diagram lines, the splitting of the HS lines, and their intensity ratio. Good agreement with theory was found for all quantities except for the intensity ratio, which is dominated by the intermediacy of the coupling of the angular momenta. The observed deviations imply that our current understanding of the variation of the coupling scheme from LS to jj across the periodic table may require some revision.Peer reviewe

Structure and triclustering in Ba-Al-O glass

Glass-forming ability in the (BaO) x(Al 2O 3) 1-x system (0≤x≤1) was investigated by using the containerless aerodynamic levitation and laser-heating method. The main glass-forming region was found to occur for 0.40(2) ≤x≤ 0.48(2), where there is insufficient oxygen to form an ideal network of corner-sharing AlO 4 tetrahedra in which the oxygen atoms are twofold coordinated, with another narrow glass-forming region at x = 0.62(2) around the eutectic composition. The glass corresponding to x = 0.4 was chosen for further investigation by using both neutron and x-ray diffraction, and a detailed atomistic model was built by applying a combination of molecular dynamics and reverse Monte Carlo methods. The results show a network structure based predominantly on corner-sharing tetrahedral AlO 4 motifs in which triclusters (OAl 3 units formed by three tetrahedral Al atoms sharing a common vertex) play an integral part, with as many as 21% of the oxygen atoms involved in these configurations. The barium ions bind to an average of 7.4 O atoms, most of which are twofold-coordinated bridging oxygen atoms. The larger size of barium compared to calcium narrows the range of glass-forming compositions in alkaline-earth aluminates such that the main glass-forming range corresponds to a regime in which an oxygen-deficient Al-O network is stabilized by the formation of triclusters

Ion and Electron Momentum Distributions from Single and Double Ionization of Helium Induced by Compton Scattering

We present the momentum distributions of the nucleus and of the electrons from double ionization of the helium atom by Compton scattering of photons with hν=40  keV. We find that the doubly charged ion momentum distribution is very close to the Compton profile of the nucleus in the ground state of the helium atom, and the momentum distribution of the singly charged ion to give a precise image of the electron Compton profile. To reproduce these results, nonrelativistic calculations require the use of highly correlated initial- and final-state wave functions

Hole depletion and localization due to disorder in insulating PrBa2Cu3O7-d: a Compton scattering study

The (mostly) insulating behaviour of PrBa2Cu3O7-d is still unexplained and even more interesting since the occasional appearance of superconductivity in this material. Since YBa2Cu3O7-d is nominally iso-structural and always superconducting, we have measured the electron momentum density in these materials. We find that they differ in a striking way, the wavefunction coherence length in PrBa2Cu3O7-d being strongly suppressed. We conclude that Pr on Ba-site substitution disorder is responsible for the metal-insulator transition. Preliminary efforts at growth with a method to prevent disorder yield 90K superconducting PrBa2Cu3O7-d crystallites.Comment: 4 pages, 3 figures, revised version submitted to PR

Texture and crystallite microstrain development during tensile deformation of copper - simulation and comparison to experimental results

Textures formed by tensile deformation at ambient temperatures and texture induced crystallite microstrains of pure copper were simulated using the full plastic Taylor-Bishop-Hill theory and an elastic unloading process described by the linear elastic Voigt model. The results of the simulations are compared to inverse pole figures experimentally determined by X-ray diffraction and εφψ vs. sin2ψ curves experimentally determined using high energy synchrotron radiation. It is shown that the texture evolution has a strong influence on the crystallite microstrains and produces non-linear strain curves. The microstrain distribution depends on the deformation mode and the lattice plane