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981.
Inhaltsübersicht. Die Verbindungen Na6MnS4, Na6MnSe4, Na6MnTe4, K6MnS4, K6MnSe4 und K6MnTe4 wurden durch Umsetzungen von Alkalimetallcarbonaten mit Chalkogen und Mangan bzw. Mangancarbonat in einem mit Chalkogen beladenen Wasserstoffstrom erhalten. Röntgenstrukturuntersuchungen an Einkristallen ergaben, daß alle sechs Verbindungen isotyp kristallisieren (Na6ZnO4-Typ, Raumgruppe P63mc). Als charakteristische Baugruppen treten “isolierte” tetraedrische [MnX4]-Einheiten auf. Die Temperaturabhängigkeiten der magnetischen Suszeptibilitäten führen zu einem Curie-WeissVerhalten. Erst bei tiefen Temperaturen treten offensichtlich antiferromagnetische Kopplungen auf. Dabei sind die Wechselwirkungen in den Tellurverbindungen stärker als in den Schwefelverbindungen und in den Kaliumverbindungen stärker als in den Natriumverbindungen ausgeprägt. Synthesis, Structure, and Magnetic Properties of Alkali Metal Manganese Chalcogenides A6MnX4 with A Na or K and X S, Se or Te The compounds Na6MnS4, Na6MnSe4, Na6MnTe4, K6MnS4, K6MnSe4 and K6MnTe4 were synthesized by the reaction of alkali metal carbonates with chalcogen and Mn or MnCO3 in a stream of hydrogen charged with chalcogen. Structural investigations on single crystals show that all six compounds crystallize in isotypic atomic arrangements (Na6ZnO4-type, space group P63mc), which are characterized by isolated [MnX4] tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. At low temperatures there are obviously antiferromagnetic interactions increasing from the sulfides to the tellurides and from the sodium compounds to the potassium compounds. 相似文献
982.
983.
Grochola A Kowalczyk P Jastrzebski W Pashov A 《The Journal of chemical physics》2004,121(12):5754-5760
We describe a modification of the inverted perturbation approach method allowing to construct physically sensible potential energy curves for electronic states of diatomic molecules even when some parts of the potential are not adequately characterized by the experimental data. The method is based on a simple regularization procedure, imposing an additional constraint on the constructed potential curve. In the present work it is applied to the double minimum 4 (1)Sigma(u) (+) state of Na(2), observed experimentally by polarization labeling spectroscopy technique. 相似文献
984.
Zusammenfassung Durch starke Säuren werden Alkalitetraphenyloborate in Borsäure und ein Gemisch organischer Spaltprodukte zerlegt. Die entstehende Borsäure läßt sich in bekannter Weise mit 1,1-Dianthrimid photometrisch bestimmen. Eine Arbeitsvorschrift zur indirekten spektralphotometrischen Bestimmung von Kalium, Rubidium und Cäsium wird angegeben. Das Verfahren wurde statistisch und anhand von Beleganalysen geprüft.
Evaluations of tetraphenyloborate precipitates
Summary The alkali tetraphenyloborates are decomposed by strong acids into boric acid and a mixture of organic fission products. The resulting boric acid can be determined photometrically in known manner with 1,1-dianthrimide. A working procedure for the indirect spectrophotometric determination of potassium, rubidium and cesium is given. The method was tested statistically and with reference to check analyses.相似文献
985.
The first synthesis of two porphyrin-phthalocyanine heterodimers with a direct triple bond linkage between the macrocycles, designed for the study of photo-induced energy and electron transfer processes, is presented along with preliminary ground state and fluorescence spectroscopic data. 相似文献
986.
The proton chemical shift tensor of the hydroxyl proton in calcium hydroxide has been measured using multiple pulse NMR techniques. The tensor is axially symmetric with susceptibility corrected components σtT = ?9.3 ± 1 ppm and ppm relative to TMS. 792 79 相似文献
987.
W.E. Falconer G.R. Jones W.A. Sunder M.J. Vasile Annabel A. Muenter T.R. Dyke W. Klemperer 《Journal of fluorine chemistry》1974,4(2):213-234
Most known non-radioactive pentafluorides have been examined by molecular-beam mass spectrometry and by the deflection of molecular beams in inhomogeneous electric fields. Extensive association of the vapors occurs for all but the lighter pentafluorides and the interhalogens. The interhalogen pentafluorides are strongly polar, consistent with the accepted C4v symmetry. The transition-metal and Group V pentafluorides are all non-polar, except VF5 and CrF5 for which temperature-dependent polarity is observed. However, uncertainty exists as to whether these observations are applicable to monomeric pentafluorides in all cases. Mass-spectral cracking patterns are presented for all species. 相似文献
988.
W. Koenig F. -W. Richter J. Ch. Bode B. Meinel 《Journal of Radioanalytical and Nuclear Chemistry》1980,58(1-2):327-339
Multi-element-analysis by PIXE in respect to medical applications is discussed. Examples of trace-element determinations in
liver tissues are given, demonstrating the applicability and usefulness of this rather new analytical technique.
相似文献
989.
G. J. De Jong U. A. Th. Brinkman W. Th. Kok 《Journal of Radioanalytical and Nuclear Chemistry》1977,35(2):245-252
An investigation has been made on the system liquid anion-exchanger-Cd(II)-NCS−. The influence of the acidity and thiocyanate concentration of the aqueous phase on the extraction has been studied. Using
various methods of analysis, it has been shown that the complex anion present in the organic extracts is Cd(NCS)
4
2−
. Details are given concerning the removal of traces of Zn(II) from Cd(II)-containing solutions, and the quantitative separation
of Cd(II) from Cr(III). 相似文献
990.
The United States Geological Survey reference sample AGV-1 andesite, and three alkaline rocks from the apatite mine of Jacupiranga, Brasil, were analyzed by thermal neutron activation analysis using destructive and non-destructive methods, and high resolution Ge(Li) gamma-ray detectors. One of the rocks, a carbonatite, was also analyzed by instrumental activation analysis with epithermal neutrons. A greater number of elements can be determined using the radiochemical separation, but the precision and accuracy attained by INAA and RNAA were of the same order for most of the elements analyzed. Epithermal activation was more advantageous for tantalum, terbium and holmium. Comparison of the analytical results for USGS reference sample (AGV-1) with the data published by others gave good agreement. Statistical tests used for comparison of the results of destructive and non-destructive methods, as well as other results are presented. 相似文献