search results

The title compound, [Co(C₁₄H₁₈N₂O₆)], is the first structurally characterized example of a -ketoiminato Co^II complex without axial ligands. It adopts a square-planar cis-[CoN₂O₂] coordination geometry, and lies on a mirror plane. The planar complexes are stacked along 2₁ screw axes parallel to b to form columns, the CoCo distance in the column being 3.5213 (2) Å.

A low-energy positron beam is a unique probe of Fermi surfaces, defects, surfaces and interfaces. In high-energy electron and positron storage rings (E > 6 GeV) it is possible to generate intense synchrotron radiation with 1-3 MeV photons by installing a high-field superconducting wiggler. The strength of the wiggler should be ~8-12 T. High-energy photons are emitted from the wiggler and converted to low-energy positrons by using a suitable target-moderator system. For an 8 GeV electron storage ring at a beam current of 100 mA, final yields are estimated to be ~10¹⁰-10¹² (slow-e⁺ s^-1) with the size of positron source ~10²-10³ cm². The possibility of increasing the brightness of the low-energy positron beam is discussed. Advantages of using synchrotron radiation for producing positrons are pointed out. The effect of a superconducting wiggler on the stored electron beam is also discussed.

A low-energy positron beam is a unique probe of materials. In high-energy electron and positron storage rings it is possible to generate intense synchrotron radiation with a photon energy of 1-3 MeV by installing a high-field (8-10 T) superconducting wiggler. High-energy photons are converted to low-energy positrons by using a suitable target-moderator system. For an 8 GeV electron storage ring at a beam current of 100 mA, final yields are estimated to be about 10⁸-10¹⁰ slow-e⁺ s^-1 or larger depending on the moderation efficiency, with the size of the positron source 10¹-10² cm². In the present work a wiggler magnetic system of 10 T is proposed. The main parameters of the superconducting wiggler are presented.

To characterize the defect sites in the near-surface and bulk phase of Li-MgO and Li-La₂O₃-MgO, XANES at Mg K-edge and La L3-edge was applied. For Li-MgO, it can be suggested that Li doping at a low content (2.5 wt%) brings about the formation of defect species only in the near-surface. This is due to the localization of doped Li ions in the surface, and thus the catalytically active species containing [Li+-O-] type center exist in the surface region. After OCM reaction, the defect species are formed in the near-surface over MgO and Li-MgO. By addition of La₂O₃ to Li-MgO (La/(Mg+La)=0.25), the structural change during the reaction is almost suppressed in the surface. In addition, the Li-La₂O₃-MgO shows higher C2 selectivity than Li-MgO.