Preparation and Crystal Structure of Re3O10

Trirheniumdecaoxide, Re₃O₁₀, was obtained by the reaction of ReO₂ and ReO₃ in an arc-melting furnace. X-ray powder diffraction revealed a tetragonal structure with space group I m2 and lattice constants a=5.171(1) and c=13.371(6) Å. The crystal structure is built up by layers of corner-sharing [ReO₅] square pyramids perpendicular to [001] with the apical oxygen pointing up and down alternatingly. These layers are interconnected by disordered [ReO₆] octahedra. Early reports on Re₂O₅ are reviewed in the light of our results.     

Fractal substructure of a nanopowder

The structural evolution of a nanopowder by repeated dispersion and settling can lead to characteristic fractal substructures. This is shown by numerical simulations of a two-dimensional model agglomerate of adhesive rigid particles. The agglomerate is cut into fragments of a characteristic size l, which then are settling under gravity. Repeating this procedure converges to a loosely packed structure, the properties of which are investigated: (a) The final packing density is independent of the initialization, (b) the short-range correlation function is independent of the fragment size, (c) the structure is fractal up to the fragmentation scale l with a fractal dimension close to 1.7, and (d) the relaxation time increases linearly with l.     

Simplified THz Instrumentation for High-Field DNP-NMR Spectroscopy

We present an alternate simplified concept to irradiate a nuclear magnetic resonance sample with terahertz (THz) radiation for dynamic nuclear polarization (DNP) experiments using the TE(01) circular waveguide mode for transmission of the THz power and the illumination of the DNP sample by either the TE(01) or TE(11) mode. Using finite element method and 3D electromagnetic simulations we demonstrate that the average value of the transverse magnetic field induced by the THz radiation and responsible for the DNP effect using the TE(11) or the TE(01) mode are comparable to that generated by the HE(11) mode and a corrugated waveguide. The choice of the TE(11)/TE(01) mode allows the use of a smooth-walled, oversized waveguide that is easier to fabricate and less expensive than a corrugated waveguide required for transmission of the HE(11) mode. Also, the choice of the TE(01) mode can lead to a simplification of gyrotron oscillators that operate in the TE(0n) mode, by employing an on-axis rippled-wall mode converter to convert the TE(0n) mode into the TE(01) mode either inside or outside of the gyrotron tube. These novel concepts will lead to a significant simplification of the gyrotron, the transmission line and the THz coupler, which are the three main components of a DNP system.     

T-REX

The potential barrier impeding the spontaneous emission of protons in the proton radioactive nuclei is calculated as the sum of nuclear, Coulomb and centrifugal contributions. The nuclear part of the proton-nucleus interaction potential is obtained in the energy density formalism using the Skyrme effective interaction that results into a simple algebraic expression. The half-lives of the proton emitters are calculated for the different Skyrme sets within the improved WKB framework. The results are found to be in reasonable agreement with the earlier results obtained for more complicated calculations involving finite-range interactions.     

Characteristic classes of star products on Marsden–Weinstein reduced symplectic manifolds

In this note we consider a quantum reduction scheme in deformation quantization on symplectic manifolds proposed by Bordemann, Herbig and Waldmann based on BRST cohomology. We explicitly construct the induced map on equivalence classes of star products which will turn out to be an analogue to the Kirwan map in the Cartan model of equivariant cohomology. As a byproduct, we shall see that every star product on a (suitable) reduced manifold is equivalent to a reduced star product.     

Bioinspired Enhancement of Superexchange: From 1,3,5-Trihydroxybenzene-Bridged to 1,3,5-Trimercaptobenzene-Bridged Trinuclear Copper(II) Complexes

An unprecedented trinucleating ligand with a central 1,3,5-trimercaptobenzene unit and its trinuclear Cu(II)(3) complex are presented. The high covalency of the difficult-to-realize Cu(II)-SR bond provides an order of magnitude increase in the superexchange interaction in comparison to its oxygen analogue.