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1Author    J. G. Correia, J. P. Araújo, J. G. Marques, A. R. Ramos, A. A. Melo, J. C. SoaresRequires cookie*
 Title    Electron-Gamma PAC: New Possibilities for NQI Studies  
 Abstract    The application of hyperfine interaction techniques to problems in solid state physics has been stead-ily growing over the last decade with the use of radioactive ion beam facilities such as ISOLDE at CERN. New applications of the e~-y Perturbed Angular Correlation (PAC) technique are underway at ISOLDE using probe nuclei with highly converted cascades. In this paper we present the motivation for extend-ing PAC experiments to elements/isotopes not usable with the conventional y-y PAC technique. Examples will be shown where the long-lived 73 As/ 73 Ge, the short lived 127 Ba/ 127 Cs and the 197m Hg/ l97 Hg decay cascades are applied to measurements of nuclear quadrupole interactions in materials. 
  Reference    Z. Naturforsch. 55a, 3—14 (2000); received September 11 1999 
  Published    2000 
  Keywords    Nuclear Techniques, Hyperfine Fields, Semiconductors, Superconductors 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0003.pdf 
 Identifier    ZNA-2000-55a-0003 
 Volume    55 
2Author    Strontiumchromate, K. Hartl, R. BraungartRequires cookie*
 Title    eine Hochtemperaturphase mit Defekt-Bariumphosphat-Struktur a High- Temperature Compound with Defect-Bariumphosphate Structure  
 Abstract    Black hexagonal platelets growing on stron-tiumoxide in the presence of chromium (III)-oxide and air at temperatures from 1250 to 1400 °C have been shown to belong to the rhombohedral space group R3m. In hexagonal orientation the elementary cell has the axes ao = 1115.8 i 0.9 pm and c0 = 4037 ± 3,6 pm and Z = 24, Dx — 4.26. Structurally the compound is closely related to Ba3(P04)2, with the excep-tion, that there are defects in the metal sub-lattice. At temperatures below 1200 °C Stron-tiumchromate(V, VI) decomposes into the dis-crete chromates(V) and -(VI). At temperatures from 113 to 338 K the compound is an electronic semiconductor with an activation energy of 0.26 eV. 
  Reference    Z. Naturforsch. 33b, 952—953 (1978); eingegangen am 1. Juni 1978 
  Published    1978 
  Keywords    High-Temperature Oxochromate, Defect Structure, Mixed-Valence Oxochromate, Semiconductor 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0952_n.pdf 
 Identifier    ZNB-1978-33b-0952_n 
 Volume    33 
3Author    Teiji Kobayasi, Hisashi NaraRequires cookie*
 Title    Core-Orthogonalization Effect in Pseudopotential Theory of the Charge Density Distribution of Valence Electrons in Semiconductors with Comments on the Effects in Momentum Space  
 Abstract    A pseudopotential calculation has been performed for the charge density distribution in Si and Ge, with the core-orthogonalization terms fully included. The state of a positron subject to the Coulomb field of the resultant electron distribution in Si is also calculated. A possible improvement of the calculated distributions of electrons and positrons in momentum space is discussed. 
  Reference    Z. Naturforsch. 48a, 193—197 (1993); received January 3 1992 
  Published    1993 
  Keywords    Charge density, Momentum density, Pseudopotential theory, Core orthogonalization, Semiconductors 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0193.pdf 
 Identifier    ZNA-1993-48a-0193 
 Volume    48 
4Author    StadeS. Nunes, S. Sulaiman, N. Sahoo, T. P. Das, M. Frank, W. Kreische, K. B. NielsenRequires cookie*
 Title    Study of the Location of Implanted Fluorine Atoms in Silicon and Germanium through Their Nuclear Quadrupole Interactions  
 Abstract    Time Differential Perturbed Angular Distribution (TDPAD) measurements of the nuclear quadrupole hyperfine parameters for 19 F* implanted into amorphous, polycrystalline and crys-talline silicon and germanium are reported and reviewed. Two signals are observed in the crystalline materials (« 35 and 23 MHz in silicon, % 33 and 27 MHz in germanium) while only one is detected in the amorphous and polycrystalline samples (ä22 MHz in silicon, «27 in germanium). Impurity sites in these materials were modeled using a Hartree-Fock cluster procedure. The Intrabond, Antibond, and Substitutional sites in the bulk were studied in both silicon and germanium. The ATOP and Intrabond Surface sites were also studied in silicon and the results extended to germa-nium. Lattice relaxation effects were incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The electronic wave functions were obtained for each optimized cluster by applying Unresctricted Hartree-Fock theory, and these wave functions were used to calculate the nuclear quadrupole hyperfine parameters at the site of the fluorine nucleus. Comparison of the theoretical hyperfine parameters to the experimental values indicates that 19 F* located in the Intrabond and Intrabond surface sites could readily explain the higher frequency signal that has been observed. 19 F* in the Antibond and the surface ATOP sites yield hyperfine parameters consistent with the low frequency signal observed in the crystalline materials and the single signal observed in the amorphous (or polycrystalline) materials. Examina-tion of these two sites, in view of other available experimental evidence including the temperature dependence of the TDPAD signals, leads to the conclusion that the lower frequency signal is due to 19 F* implants which have come to rest at the site of dangling bonds in the bulk. These dangling bonds are created as a result of damage generated in the individual collision cascades during the implantation process. 
  Reference    Z. Naturforsch. 51a, 560—564 (1996); received December 12 1995 
  Published    1996 
  Keywords    Semiconductors, Impurities, Electronic structure, Hartree-Fock, Electric field gradient 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0560.pdf 
 Identifier    ZNA-1996-51a-0560 
 Volume    51