Acetoxytropyliumbromid: Synthese,Strukturbeweis, Verhalten in Lösung

Acetoxytropyliumbromide: Synthesis, Structural Evidence, Behaviour in Solution. Acetoxytropyliumbromide ( 9 ) is formed from tropone and acetylbromide. In solution the tropylium salt equilibrates with the educts, 9 being favored at low temperature in polar aprotic solvents. The structure of the title compound has been proved by X-ray analysis, as well as by investigation of the ¹H-NMR. spectra of solutions of 9 .     

Optimum pulse repetition rates for single photon counting experiments

In the first part of this paper, the optimum pulse repetition rate (PRR) for fluorescence lifetime measurements based on time correlated single photon counting is obtained by minimizing the variance in the lifetime estimates, assuming a single exponential decay. This allow us, in the second part, to calculate the optimum pulse repetition rate for systems possessing a set of discrete repetition rates; such as synchronously pumped mode locked cavity dumped laser systems.     

Magnetic order in AVX3 (A = Rb,Cs, (CD3)4 N; X = Cl,Br, I): A neutron diffraction study

AVX₃ (A = Rb, Cs, (CD₃)₄ N; X = Cl, Br, I) crystallize in the hexagonal system, space group $\text{P6}{}_3\text{mmc}$, with chains of face-sharing VX₆ octahedra along the c-axis. This leads to a pronounced one-dimensional character of their magnetic properties with a strong antiferromagnetic exchange interaction J between nearest neighbor V²⁺ ions along these chains. All compounds except [(CD₃)₄N]VCl₃ order three-dimensionally with ordering temperatures T_c between 13 and 32 K. In the ordered phase the magnetic moments, μ, lie in the basal plane in a triangular arrangement typical for antiferromagnetic interchain interaction J′.     

Eine untere Schranke für λ1 auf Mannigfaltigkeiten mit fast negativer Krümmung

Ohne ZusammenfassungDie Arbeit wurde im Rahmen des Sonderforsehungsbereichs Theoretische Mathematik (SFB 40) an der Universität Bonn geschrieben.     

Carbon-13 NMR spectra of simple glycidic esters

The line separations from geminal and vicinal CH-couplings in simple glycidic esters are found to be within narrow ranges. They can be used for the assignment of carbon resonances and epoxide configurations.