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  • Electronic Resource  (4)
  • chemical transport  (3)
  • 23.20.En  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Anomalous behaviour of transition probabilities in75Kr (1990)
    Springer
    The European physical journal 336 (1990), S. 391-402 
    Details
    ISSN: 1434-601X
    Keywords: 27.50.+e ; 23.20.En ; 23.20.Gq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two collective bands of75Kr have been extended up to spin 21/2 using the compound reactions64Zn(14N,p2n)75Kr and50Cr(28Si, 2pn)75Kr. Spins and parities were assigned from neutron-gatedγ-ray angular distributions and excitation functions using the OSIRIS anti-Compton spectrometer. The bands are interpreted to be built on the well-deformed Nilsson states: [442] 5/2 and [301] 3/2. Energies for both bands and the order of magnitude of the mixing ratios in thef 5/2 band can be reproduced within the single-particle-plus-rotor model, while the experimentalQ(I→I−1)/Q(I→I−2) ratios, deduced from mixing ratios and branching ratios, exhibit large deviations by a factor 4 to 6 from theoretical values (which are around one). An explanation of this effect may be found by treating the two rotational bands each as a result of mixing between rotational bands of oblate and prolate states; thus explaining the large difference between B(E2,I→I−1) andB(E2, I →I−2) in the bands of75Kr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294113
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  • 2
    Electronic Resource
    Electronic Resource
    Synthese und Struktur von M4Ta18O53 (M = Th, U); die ersten Vertreter eines neuen Strukturtyps à la JahnbergProfessor Herbert Jacobs zum 60. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 640-648 
    Details
    ISSN: 0044-2313
    Keywords: Th4Ta18O53 ; U4Ta18O53 ; chemical transport ; crystal structure ; Jahnberg-structure-family ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of M4Ta18O53 (M = Th, U); the First Representatives with a New Structure Type à la JahnbergColorless {brownblack}, hexagonal crystals of Th4Ta18O53 {U4Ta18O53} were obtained by chemical transport. Several mixtures of powders were used as starting materials for chemical transport reactions. Cl2 or TaCl5/Cl2 were applied as transport agents in several temperature gradients. The lattice constants are a = 6.2554(5) Å {6.253(1) Å}, c = 27.709(5) Å {27.609(6) Å} and Z = 1. Structure determination in the space group P63/mcm (no. 193) let to R1 = 0.0269 (wR2 = 0.0629) {R1 = 0.0295 (wR2 = 0.0674)}. Thorium as well as Uran is surrounded by oxygen like an trans-bis-capped octahedron (CN = 8) and Tantalum1 and Tantalum2 like pentagonal-bipyramids (CN = 7). The formula (Th2O3)2(Ta3O8)6 corresponds to the principle of building for the ideal construction. Because of necessarity of valence compensation the number of O-atoms in the real structure is diminished by one.The Th—O- and U—O-coordination polyhedra are for themselves arranged to o-layers and the Ta1—O- and Ta2—O-bipyramids for each other to p-layers. These layers are edge linked along the c-axes with a sequence of p-p-p-o-p-p-p-o. In fact of this these compounds are the first examples of the new structure type p-p-p-o as a member of a structure-family first described by Jahnberg. The various members differ in the sequence of layers with octahedral (o) and pentagonal-bipyramids (p).
    Notes: Durch chemischen Transport mit Cl2 oder TaCl5/Cl2 als Transportmittel wurden ausgehend von entsprechenden Ausgangsbodenkörpern im Temperaturgefälle T2 → T1 (z. B. 1000 °C → 980 °C) farblose {braunschwarze}, hexagonale Einkristalle von Th4Ta18O53 {U4Ta18O53} mit den Gitterkonstanten a = 6,2554(5) Å {6,253(1) Å}, c = 27,709(5) Å {27,609(6) Å} und Z = 1 erhalten. Die Strukturaufklärung in der Raumgruppe P63/mcm (Nr. 193), die bei R1 = 0,0269 (wR2 = 0,0629) {R1 = 0,0295 (wR2 = 0,0674)} konvergierte, ergab für Th {U} CN = 8 sowie Ta1 und Ta2 CN = 7. Th {U} ist in Form eines trans-bis-bekappten Oktaeders, Ta1 und Ta2 pentagonal-bipyramidal von Sauerstoff umgeben. Dem Bauprinzip der Idealstruktur entspricht die Formulierung (Th2O3)2(Ta3O8)6, die für die Realstruktur aufgrund des Valenzausgleiches um ein O-Atom zu vermindern ist.Die Th—O-{U—O-} Koordinationspolyeder sind in o-Schichten, die Ta1—O- und Ta2—O-Bipyramiden jeweils für sich in p-Schichten so angeordnet, daß sich eine Schichtabfolge p-p-p-o-p-p-p-o in c-Richtung ergibt. Hiernach sind die beiden Verbindungen als erste Vertreter einer neuen Variante der von Jahnberg erstmals beschriebenen Strukturen anzusehen, für die verschiedene Schichtabfolgen aus oktaedrischen (o) und pentagonal-bipyramidalen (p) Baueinheiten charakteristisch sind.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220412
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  • 3
    Electronic Resource
    Electronic Resource
    Darstellung, Kristallstruktur und elektronenmikroskopische Untersuchung von UNb6O16 - einem neuen niobreichen Oxid im System U/Nb/O (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1056-1065 
    Details
    ISSN: 0044-2313
    Keywords: UNb6O16 ; chemical transport ; crystal structure ; HRTEM ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation, Crystal Structure and Electron Microscopic Investigation of UNb6O16 - a New Niobium-rich Phase in the System U/Nb/OPowdery UNb6O16 was produced by heating (1 000°C or 1 100°C; evacuated silica tube) mixed powders of UO2, NbO2 and Nb2O5 (1:2:2). Single-crystals of UNb6O16 were obtained by chemical transport in a small temperature gradient (1 000°C → 990°C; transport agent NH4Cl). The lattice constants are a = 22 339(4) Å; b = 3.7750(6) Å; c = 7.249(3) Å; β = 97.61(3)° and Z = 2. The structure determination (space group C2) let to R = 0.026 (Rw = 0.026). Eight oxygen atoms surround U4+ like a trans-bis-capped octahedron, Nb4+ and Nb5+ are coordinated distorted octahedraly. The structure was checked and the occupation of the positions O8 and O9 was clarified with the program MAPLE4 [3]. A through focus series of high resolution transmission electron microscopic images was obtained which is in acceptable agreement with images calculated on the basis of the multi-slice method.
    Notes: Die Darstellung von pulverförmigem UNb6O16 gelingt durch Festkörperreaktion (1 000°C oder 1 100°C; evakuierte Quarzglasampulle) aus UO2, NbO2 und Nb2O5 (Gemenge 1:2:2). Schwarze Einkristalle sind durch chemischen Transport in einem geringen Temperaturgefälle (1 000°C→990°C; Transportmittel NH4Cl) zugänglich. UNb6O16 hat die Gitterkonstanten a = 22,339(4) Å; b = 3,7750(6) Å; c = 7,249(3) Å; β = 97,61(3)°; Z = 2. Die Strukturverfeinerung anhand von Einkristalldaten (RG C2) konvergierte bei R = 0,026 (Rw = 0,026). Die Metall-Sauerstoff-Koordinationspolyeder um Uran und Niob sind stark verzerrt. U4+ kann als dodekaedrisch bzw. trans-bis-bekappt oktaedrisch (CN = 8), Nb4+ und Nb5+ als oktaedrisch (CN = 6) koordiniert angesehen werden. Mit dem Programm MAPLE4 [3] konnte die Struktur überprüft, sowie die Halbbesetzung der Punktlagen O8 und O9 geklärt werden. Eine Defokusserie hochaufgelöster elektronenmikroskopischer Durchstrahlungsaufnahmen wurde mit rechnerischen Kontrastsimulationen verglichen.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200619
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  • 4
    Electronic Resource
    Electronic Resource
    Darstellung und Struktur von Th2Ta6O19, dem ersten Beispiel einer „Jahnberg-Struktur“ mit M = M4+ (M = Th4+); mit einer Anmerkung zu LaNb7O19In memoriam Professor Wilhelm Klemm (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 67-75 
    Details
    ISSN: 0044-2313
    Keywords: Th2Ta6O19 ; LaNb7O19 ; chemical transport ; crystal structure ; “Jahnberg-structure-family” ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Crystal Structure of Th2Ta6O19, the First Example of a “Jahnberg-Structure” with M = M4+ (M = Th4+); with a Note to LaNb7O19Colorless, hexagonal crystals of Th2Ta6O19 were obtained by chemical transport in the temperature gradient 1000°C → 980°C using a mixture of ThO2, ZrO2 (or HfO2) and Ta2O5 (1 : 2 : 2) as starting material and Cl2, ZrCl4 or HfCl4 as transport agents. The lattice constants are a = 6.275(1) Å, c = 19.968(6) Å and Z = 2. Structure determination in the space group P63/mcm (no. 193) let to R1 = 0.032 (wR2 = 0.074). Thorium is surrounded by oxygen like an transbis-capped octahedron (CN = 8) and tantalum like a pentagonal bipyramid (CN = 7).Both coordination polyhedra are for themself arranged to layers (Th to o-, Ta to p-layers) so that in the direction of the c-axes a sequence of layers like p-p-o-p-p-o appears. Therefore the compound is a new representative of the structures described by Jahnberg.
    Notes: Durch chemischen Transport, ausgehend von Gemengen aus ThO2, ZrO2 (bzw. HfO2) und Ta2O5 (1 : 2 : 2) und mit Cl2, ZrCl4 oder HfCl4 als Transportmittel, wurden im Temperaturgefälle 1000°C → 980°C farblose, hexagonale Einkristalle von Th2Ta6O19 mit den Gitterkonstanten a = 6,275(1) Å, c = 19,968(6) Å und Z = 2 erhalten. Die Strukturaufklärung in der Raumgruppe P63/mcm (Nr. 193), die bei R1 = 0,032 (wR2 = 0,074) konvergierte, ergab für Th CN = 8 und Ta CN = 7. Thorium ist in Form eines transbis-bekappten Oktaeders, Tantal pentagonal-bipyramidal von Sauerstoff umgeben.Beide Koordinationspolyeder sind für sich in Schichten (Th in o-, Ta in p-Schicht) so angeordnet, daß sich eine Schichtabfolge p-p-o-p-p-o in c-Richtung ergibt. Demnach ist die Verbindung als neue Variante der von Jahnberg beschriebenen Strukturen anzusehen.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220111
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