TR-LII for sizing of carbon particles forming at room temperature

Time-resolved laser-induced incandescence (TR-LII) was applied for the determination of particle sizes during carbon-particle formation from supersaturated atomic carbon vapor that was generated by laser photolysis of carbon suboxide (C₃O₂) at room temperature. Thus, the solid carbon particles were formed under hydrogen-free conditions. The TR-LII technique was used for in situ size measurement of growing carbon particles and samples of final particles were analyzed by transmission electron microscopy (TEM). It was found that the particles grow to a final size of 4–12 nm within 0.02–1 ms. The properties of the obtained particles depend on the initial conditions in the reaction volume, i.e. concentration of carbon suboxide, pressure and type of gas diluter, photolysis wavelength, and laser pulse energy. The comparison of TR-LII and TEM particle sizing results yields information about the effective thermal energy accommodation coefficients for He, Ar, CO, and C₃O₂ molecules on carbon particles. PACS 61.46.Df; 07.60.-j; 78.70.-g     

CZE separations of basic proteins at low pH in fused silica capillaries with surfaces modified by silane derivatization and/or adsorption of polar polymers

Mixtures of several basic proteins have been used to test CZE capillaries with surfaces modified by new pretreatment procedures; the performance obtained has been compared with that achieved using capillaries treated by procedures described in the literature. It has been shown that addition of non-ionic polyvinylalcohols (PVA) to CZE buffer solutions deactivates even bare, i.e. untreated, fused silica surfaces and renders them suitable for separations of basic proteins. The performance obtained from such surfaces was comparable with that of capillaries modified by the more elaborate procedures of etching, silanol derivatization, and/or adsorptive coating (again with polymers). A home-made device is described which enables derivatization and coating reactions to be performed on fused silica capillaries under an inert atmosphere, i.e. one free from oxygen and water.     

The dipole moment, polarizabilities, and first hyperpolarizabilities of HArF. A computational and comparative study

The electronic and vibrational contributions to the dipole moment, polarizabilities, and first hyperpolarizabilities of HArF are reported. These have been computed by using a series of systematically built basis sets and a hierarchy of computational methods. HArF has a very large first hyperpolarizability along the z axis. This has been rationalized by invoking the difference in the electronic structure between the ground and the first excited state. The argon fluorohydride has been recently derived and characterized. The present study provides complementary data for the understanding of the electronic structure of this interesting argon derivative.     

Röntgenstrahlenbeugung bei hohen Temperaturen zur Untersuchung der thermischen Ausdehnung von MnSe und MnSe2

Zusammenfassung Durch Röntgenstrahlenbeugung mit Hilfe einer 190 mm Unicam-Hochtemperaturkamera wurde die thermische Ausdehnung von MnSe und MnSe₂ von Zimmertemperatur bis 710° bzw. 522° C untersucht. Der thermische Ausdehnungskoeffizient wurde aus den Meßdaten nach der Methode der kleinsten Fehlerquadrate erhalten und beträgt für MnSe: =24,5·10^–6°C^–1 (94–450° C) und =14,3·10^–6°C^–1 (450–710° C). Die Ausdehnung von MnSe₂ verläuft bis zum Bereich, in dem Zersetzung eintritt, linear. Die Methode der kleinsten Fehlerquadrate ergibt den Wert =20,0·10^–6°C^–1 (73–522° C).

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High temperature X-ray studies of the thermal expansion ofMnSe andMnSe ₂

The thermal expansion of MnSe and MnSe₂ has been studied above room temperature up to 710° and 522° C, resp., by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The thermal expansion coefficients, , obtained from a linear least-squares analysis of the data are for MnSe: =24.5·10^–6°C^–1 (94–450° C) and =14.3·10^–6°C^–1 (450–710° C). The expansion of MnSe₂ is linear up to the temperature range of decomposition. A least-squares analysis yields a value for of 20.0·10^–6°C^–1 (73–522° C).

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Mit 2 Abbildungen

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Herrn Prof.H. Nowotny gewidmet.     

Purification and analysis of partially alkylated cyclodextrins by liquid and gas chromatography

Complex mixtures of partially alkylated cyclodextrins can be analyzed by both HPLC and high temperature capillary GC. Because of the limited efficiency of LC, suitable analytical and preparative separations can be achieved only with systems of carefully optimized selectivity. Using LC it has been possible to isolate and purify single cyclodextrin species from very complex mixtures of components which contain unreacted hydroxyl groups in addition to the alkoxy groups. Analysis of the reaction mixtures and of fractions taken from LC separations can be performed with advantage by high resolution capillary GC at high temperatures between 300 and 400 °C. The thermal stability of partially alkylated cyclodextrins in high temperature GC is considerably increased by trimethylsilylation of the free hydroxyl groups. Fast atom bombardment mass spectrometry and proton NMR were used to identify species isolated from the preparative LC separations.     

Steroids and sex hormones. Quassinoid bitter principles. I. 1-oxo-2-methoxy-4 alpha-methyl-17 beta-hydroxy-delta2-5 alpha-androstene as a model for the ring a structure of quassine]

Starting from 3-oxo-17β-hydroxy-Δ¹-5α-androstene (2b) the preparation of 1-oxo-2-methoxy-4α-methyl-17β-hydroxy-Δ²-5α-androstene (9), a compound with the ring A structure of quassine (1) is described. The key problem of the reaction sequence is shown to be the monomethylation at C(4).     

The temperature-composition phase diagram of the HgTe?HgI2 pseudobinary system on the HgTe rich side

The temperature-composition phase diagram of the HgTe? HgI₂ system was determined from 0 to 45 Mol-% HgI₂ between 25 and 670°C using Debye-Scherrer powder X-ray diffraction techniques and differential thermal analysis. Solid solutions of HgTe and HgI₂ with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7 ± 0.8 Mol-% HgI₂ in HgTe at 501 ± 5°C. The known monoclinic compound Hg₃Te₂I₂ is formed by a peritectic reaction upon cooling at 501 ± 5°C, with the peritectic point at approximately 37 ± 4 Mol-% HgI₂.