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Anomalous behaviour of transition probabilities in75Kr (1990)

Skoda, S. ; Wood, J. L. ; Eberth, J. ; [et al.]

Springer

The European physical journal 336 (1990), S. 391-402

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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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Darstellung, Kristallstruktur und elektronenmikroskopische Untersuchung von UNb6O16 - einem neuen niobreichen Oxid im System U/Nb/O (1994)

Busch, J. ; Hoffmann, G. ; Gruehn, R.

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 620 (1994), S. 1056-1065

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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.