On the origin of 1.5 μm luminescence in porous silicon coated with sol–gel derived erbium-doped Fe2O3 films

Sol–gel derived Fe₂O₃ films containing about 10 wt% of Er₂O₃ were deposited on porous silicon by dipping or by a spin-on technique followed by thermal processing at 1073 K for 15 min. The samples were characterized by means of PL, SEM and X-ray diffraction analyses. They exhibit strong room-temperature luminescence at 1.5 μm related to erbium in the sol–gel derived host. The luminescence intensity increases by a factor of 1000 when the samples are cooled from 300 to 4.2 K. After complete removal of the erbium-doped film by etching and partial etching the porous silicon, the erbium-related luminescence disappears. Following this, luminescence at 1.5 μm originating from optically active dislocations (“D-lines”) in porous silicon was detected. The influence of the conditions of synthesis on luminescence at 1.5 μm is discussed.     

Biomimetic Explorations Towards the Bisorbicillinoids: Total Synthesis of Bisorbicillinol, Bisorbibutenolide, and Trichodimerol

Strikingly simple cascade dimerization sequences can be used to assemble the complex frameworks of bisorbicillinoids such as bisorbicillinol (1), bisorbibutenolide (2), and trichodimerol (3). The mechanistic facets of the biomimetic total syntheses of these bioactive natural products were also explored. Inspection of the unique molecular architecture of these compounds reveals that they are likely to be assembled in nature by a dimerization of two oxidized forms of sorbicillin.     

Darstellung und Eigenschaften einiger neuer Arsenat- und Vanadat-Halogen-Apatite

Preparation and Properties of Some New Arsenate and Vanadate Halogen Apatites The preparation of new apatite-like compounds of the composition Na₂Nd₂Pb₆(RO₄)₆X₂ (with R = As, V and X = Cl, Br and also R = P and X = Br) is reported. Crystallographic data for these as well as for the already known Na₂Nd₂Pb₆(PO₄)₆Cl₂ are determined from the corresponding X-ray powder diagrams. Also the infrared and Raman spectra were recorded and briefly discussed.     

Abschätzung mittlerer Schwingungsamplituden der Metall—Sauerstoff-Bindungen einiger Hexaoxometallate

Mean amplitudes of vibration of a series of hexaoxometalates have been estimated using an approximation method and recently reported spectroscopic data arising from the study of the respective lithium salts.     

$\delta$-pairing forces and collective pairing vibrations

The collective pairing Hamiltonian is obtained in the framework of the generator coordinate method in the Gaussian overlap approximation with a slightly modified BCS function used as a generator function. The collective variable , measuring the monopole moment of the pairing field, and the gauge transformation angle are chosen as generator coordinates. The vibrational ground states are calculated by diagonalisation of the collective pairing Hamiltonian in the harmonic-oscillator basis.Received: 28 April 2003, Revised: 1 October 2003, Published online: 18 June 2004PACS: 21.30.-x Nuclear forces - 21.60.Ev Collective models     

Isolation and characterization of kallosin A,a novel rearranged pseudopterane diterpenoid from the Caribbean sea plume Pseudopterogorgia kallos (Bielschowsky)

The Caribbean alcyonacean Pseudopterogorgia kallos is shown to contain a novel rearranged pseudopterane diterpene, kallosin A (1), possessing several unusual structural features. In addition to having two distinct 2(3H)- and 2(5H)-furanone moieties, kallosin A is based on a new carbon skeleton. The structural assignment of 1 was based mainly on 1D and 2D NMR spectral data and was further supported by accurate mass measurement and single-crystal X-ray diffraction analysis.     

Neutron diffraction structure of Y2V10O28·24H2O at 297 and 60 K

The structure of yttrium-decavanadate-24-hydrate, [Y₂V₁₀O₂₈·24H₂O], was determined by neutron diffraction at temperatures of 297 and 60 K. Space group P-1, triclinic, Z = 2; at 297 K : a = 9.36(1), b = 9.86(1), c = 23.53(3) Å, = 98.79(2), = 98.15(2), = 89.30(2), V = 2123(5); at 60 K : a = 9.19(3), b = 9.85(3), c = 23.31(12) Å, = 99.03(3), = 98.99(6), = 89.39(6)°, V = 2058(13). Final R factors of 10 and 9.4% were obtained using 1955 and 1100 observed structure factors at both temperatures, respectively. The position of the 24 water molecules was determined and the characteristics of the hydrogen bonds were analyzed at both temperatures.