| | 4 | Author
| Wolfgang Flossmann, Herbert Zehner, Adolf Müller | Requires cookie* | | | Title
| Radicals Produced in Single Crystals of Thymine Derivatives by UV and X-Rays  | | | | Abstract
| Single crystals o f anhydrous thym ine (T), thym ine monohydrate (T ■ H 20) , 5,6-dihydrothym ine (T H 2), 1-methylthymine (mT) and thym idine (dT) were irradiated with X-rays and UV between 77 K and 300 K. Six types o f radicals were analyzed by ESR-spectroscopy at 9.5 G H z and 35 G H z after exposure to X-rays. The anion radical occurred only in T • H 20 at 77 K, the 4-yl radical only in T H 2 at 77 K and the 1-yl radical only in T between 77 K and 300 K. The 6 -yl radical was found in T, T H 2 and mT. It was converted into the 5-yl radical irreversibly by heat or white light (A < 600 nm). The 5-yl radical appeared in all compounds at room temperature. The highest thermal stability was found for the 7-yl radical which was present at room temperature in all compounds except T H 2 . U V -irradiation (A = 320 nm) produced radicals only in three crystals (T, T H 2 , dT). In T the 5-yl radical was found after exposure at 300 K, and two other radicals, 1-yl and 7-yl, at 77 K. A lso at 77 K, the 7-yl radical was present in dT and the 5-yl radical in TH 2 and dT. | | | |
Reference
| Z. Naturforsch. 35c, 20—2 (1980); received July 23 1979 | | | |
Published
| 1980 | | | |
Keywords
| Radicals, Single Crystals, Thym ine, X-Rays, ESR | | | |
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| | | | | TEI-XML for
| default:Reihe_C/35/ZNC-1980-35c-0020.pdf | | | | Identifier
| ZNC-1980-35c-0020 | | | | Volume
| 35 | |
| 5 | Author
| R. Zaleski, Z. Jakubas, L. Galewski, Sobczyk | Requires cookie* | | | Title
| | | | | Abstract
| Dielectric. DSC and preliminary X-ray diffraction studies on [(C2H5)4N]3Sb2Br9 (TEABA) and [(C2H5)4N]3Bi2Br9 (TEABB) are reported. The compounds are isomorphous, space group P6322. The static electric permittivity measurements on single crystals in the temperature range 220 290 K revealed that both compounds show two distinct dielectric anomalies; TEABA at Tcl = 258 K and Tc2 = 252 K, while TEABB at Tcl= 265 K and Tcl = 248 K. The DSC studies show only one anomaly of first order at TcX =258 K for TEABA, and TcX =266 K for TEABB. These transitions are pre sumably related to a freezing of the reorientational motion of the tetraethylammonium cations. S tr u c tu r a l P h a s e T ra n s itio n s in |(C 2H 5)4N ] 3S b 2B r 9 a n d |(C 2H 5) 4N |3B i2B r 9 | | | |
Reference
| Z. Naturforsch. 44a, 1102 (1989); received May 11 1989 | | | |
Published
| 1989 | | | |
Keywords
| Alkylammonium halogenoantimonates, Bismuthates, Phase transition Dielectric, DSC, Single crystals | | | |
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| default:Reihe_A/44/ZNA-1989-44a-1102.pdf | | | | Identifier
| ZNA-1989-44a-1102 | | | | Volume
| 44 | |
| 6 | Author
| P. De, La Presa, K. P. Lieb, M. Uhrmacher, L. Ziegeler | Requires cookie* | | | Title
| Perturbed Angular Correlation Studies in SrTi0 3 Single Crystals | | | | Abstract
| The quadrupole hyperfine interactions of 11 'Cd/ 111 In probe nuclei in single-crystalline SrTi0 3 perovskite samples were investigated using Perturbed Angular Correlation spectroscopy. Three electric field gradients were detected and their fractions and hyperfine parameters were measured in the temperature range from 26 to 700 K. The fraction / 0 having a vanishing quadrupole frequency, as expected for 111 Cd on substitutional sites in a cubic lattice, starts to develop around 300 K and reaches 100% at 700 K. Two well-defined EFG's having closely lying quadrupole frequencies and asymmetry parameters of cj qi = 49.1(3) Mrad/s, 77, = 0.10(2) and u Q2 = 51.8(3) Mrad/s, r] 2 = 0.12(2), at room temperature, were identified in the temperature range from 250 to 530 K, and their (100) orientation in the lattice was determined. They are associated with electronic defects at the probe atoms. | | | |
Reference
| Z. Naturforsch. 55a, 237—241 (2000); received August 24 1999 | | | |
Published
| 2000 | | | |
Keywords
| Perturbed Angular Correlations, SrTi0 3, Single Crystal, Electronic Defects, Perovskite | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0237.pdf | | | | Identifier
| ZNA-2000-55a-0237 | | | | Volume
| 55 | |
| 7 | Author
| Alexandra Atzesdorfer, Klaus-Jürgen Range | Requires cookie* | | | Title
| Sodium Metaperrhenate, N aR e04: High Pressure Synthesis of Single Crystals and Structure Refinement | | | | Abstract
| Single crystals of sodium metaperrhenate, N a R e 0 4, have been obtained by oxidation of rhe nium metal with sodium nitrate under high pres sure-high temperature conditions (m odified Belt-type apparatus, 4 kbar, 400 °C, Au-capsules). The crystals are tetragonal, space group 14^0, with a = 5.3654(4), c = 11.732(2) A and Z = 4. The struc ture was refined to R -0.026, Rw = 0.013 for 382 unique, absorption-corrected reflections. The scheelite-type structure for N a R e 0 4, pro posed by Beintema in 1937, could be confirmed. It consists of isolated R e 0 4 tetrahedra (R e -O = 1.728(2) A), connected by N aO s dodecahedra (< N a -0 > = 2.582(2) Ä). | | | |
Reference
| Z. Naturforsch. 50b, 1417—1418 (1995); received April 24 1995 | | | |
Published
| 1995 | | | |
Keywords
| Sodium Metaperrhenate, Single Crystals, High Pressure Synthesis, Structure Refinem ent | | | |
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| default:Reihe_B/50/ZNB-1995-50b-1417_n.pdf | | | | Identifier
| ZNB-1995-50b-1417_n | | | | Volume
| 50 | |
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