Weak decays of heavy mesons in the instantaneous Bethe Salpeter approach

In the framework of the instantaneous Bethe Salpeter equation we investigate weak decays ofB andD mesons. Mesons are described asq $\bar q$ states interacting via a mixture of a scalar and a vector confining kernel and a one gluon exchange. The model parameters are fixed by a fit to the meson mass spectrum including also the light mesons. We calculate form factors and compare our results to the pole dominance hypothesis. From a fit to ARGUS and CLEO data onB→D ^*?v semileptonic decay we extract the Cabbibo Kobayashi Maskawa matrix element to beV _cb =(0.032 ± 0.003)(1.49ps/τ _b )^1/2 The Isgur Wise function is calculated utilizing the heavy quark mass limit. Finally, we give some results on nonleptonic decays.     

Sodium self-diffusion coefficient in sodium silicate glass by quasielastic neutron scattering

Using pulsed neutrons of 19.8 Å wavelength a quasielastic line broadening as low as 0.03 eV (FWHM) has been observed due to Na⁺ diffusion in the glass Na₂O·2SiO₂. From the linewidths a Na⁺ self-diffusion coefficient of 3.1·10^–8 cm²/s at 420°C was obtained in excellent agreement with the diffusion coefficient determined for the same sample batch using²²Na radioactive tracers. The experimental Q dependence of the quasielasic linewidths gives a hint for deviations from a purely random walk in an ionic glass.     

Discrimination ofn=2→2 UV transitions of he-like ions in a recoil light source

Neon and argon recoil ions were produced by collisions with 5.9 MeV/amu uranium projectiles andΔn=0 ultraviolet transitions from the metastable 1s2p ³ P _0,2 levels of the target ions were measured in delay to the pulsed projectile beam.     

Internal dynamics of flexible molecules: Cyclohexane

Summary The international motions of a single cyclohexane molecule are studied by molecular dynamics calculations. Classical trajectories are calculated by integrating Newton's equation of motion. The potential functions used are essentially the same as in Allinger's MM2 program which is widely applied for calculations on conformational energies of organic molecules.Geometries and relative energies are reported for all stable low energy conformers and some transition states of cyclohexane. Vibrational frequencies of classical oscillations of individual bonds — computed for ethane as reference system — are close to the experimental values.Two trajectories of the molecular dynamics of cyclohexane were simulated. In the first we were able to follow the process of ring inversion: chair twisted forms inverted chair. The reaction path is analysed in detail and compared with static approaches. The second trajectory shows the correlated reorientation of the possible twisted forms alone. This process is known as pseudorotation.Dedicated to Prof. Dr. Karl Schlögl     

Intercalation of Benzamide into Kaolinite

Well-crystallized kaolinite (K) was initially reacted at 60 degrees C with a water/dimethylsulfoxide (DMSO) mixture and the resulting intercalation derivative (K-DMSO) was characterized by powder X-ray diffractometry (PXRD), thermal analysis (simultaneous TG and DSC), and Fourier-transformed infrared spectroscopy (FTIR). Benzamide crystals were then melted with the K-DMSO derivative at 140 degrees C for 4 days, when a gradual displacement of DMSO by benzamide was observed within the interlayer spacing of the modified kaolinite. The resulting material, after extensive washing with acetone, was characterized and compared to the results obtained previously for the K-DMSO composite. Benzamide intercalation proceeded by gradual displacement of DMSO molecules until completion. The structural stabilization of the K-BZ derivative was explained through the establishment of hydrogen bonds between the carbonyl oxygen atoms of the intercalated benzamide and aluminol groups present at the surface of the kaolinite layer. The interlamellar spacing of K-BZ was shown to be possibly occupied by benzamide molecules that were located at a 68 degrees orientation in relation to the layer surface. Unlike most intercalation molecules such as DMSO, variations in the interplanar spacing of kaolinite were consistent with the nonkeying of any other part of the molecule between the aluminosilicate interlayers. Copyright 2000 Academic Press.     

Zur Struktur von N-Benzoylthiobenzamid

Structure of N-Benzoylthiobenzamide N-Benzoylthiobenzamide forms two polymorphic modifications of which the crystal and molecular structures have been determined by X-ray structure analysis. In both modifications the molecules exist as NH tautomeres, but there are differences with regard to their rotameric configurations. In the monoclinic modification both symmetry independent molecules have a Z,Z′ configuration. The triclinic modification also contains two symmetry independent molecules, but now a Z,Z′ and an E,Z′ configuration exist. All four molecules deviate appreciably from planarity. The results of both structure determinations are compared with each other and with the structure of monothiodibenzoylmethane.     

ESCA-untersuchungen zur ladungsverteilung in alkylierten thioharnstoffderivaten und verwandten thiocarbonylverbindungen

The S 2p, N 1s and C 1s electron binding energies of some substituted thiourea derivatives, isothiouronium salts, thiazolthiones, 1,3,5-thiadiazin-2-thiones and 1,3,5-thiadiazinium salts have been measured using the X-ray photoelectron spectroscopy (ESCA). From binding energy shifts information concerning the charge distribution on the atoms in the molecules was obtained. The positive charge of the isothiouronium salts was found to concentrate on carbon and nitrogen atoms. The charge of the 1,3,5-thiadiazinium cations was found to be delocalized demonstrating the pseudoaromatic character of the electronic system.     

S-(N-(Thiocarbamoyl)benzimido)-dithiocarbamidsäureester

Zusammenfassung Die Synthese der Titelverbindungen3 (R ¹=R ²=C₂H₅;n-C₄H₉) durch Reaktionen von N-(N,N-Diethylthiocarbamoyl)-benzimidoylchlorid (2) mit Natriumdialkyldithiocarbamaten (1) in Aceton wird beschrieben. Die niedrigen Ausbeuten (bis 25% d.Th.) sind durch Nebenreaktionen bedingt. Die Strukturen der Verbindungen werden durch IR-,¹H-NMR-,¹³C-NMR-und Massenspektren bestätigt. Nebenreaktionen werden¹³C-NMR-spektroskopisch verfolgt und die Ergebnisse diskutiert.

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S-(N-(thiocarbamoyl)benzimido)dithiocarbamic esters

Summary The synthesis of the title compounds3 (R ¹=R ²=C₂H₅;n-C₄H₉) by reactions of N-(N,N-diethylthiocarbamoyl)benzimidechloride (2) with sodiumdialkyldithiocarbamates (1) in acetone is described. The low yields (<25%) are caused by the occurrence of side reactions. The structures of the compounds were confirmed by IR,¹H and¹³C NMR, and mass spectroscopy. Side reactions were detected by¹³C NMR spectroscopy; the results are discussed.