Temperature dependence of the muon Knight shift in graphite measured using a μSR\times 2 method

We describe a simple method by which time differential μSR spectra are collected on two different samples simultaneously. One application is to make accurate measurements of the muon precession frequency in a sample relative to a reference. As an example we report precise measurements of the muon Knight shift on HOPG graphite with H parallel to \hat c as a function of temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ueber gasanalytische Methoden und Apparate

Ohne Zusammenfassung     

Chemoenzymatic synthesis of discotic liquid crystals

Acylations at the 6-position of alkyl glycosides were obtained using the esterification potential of lipases. Thus, sugars with two alkyl chains result showing columnar discotic phases. The correlation between the configuration of the sugar moieties and the different clearing points can be understood on the basis of simple stereochemical assumptions.     

Study of transient thermal surface processes

Summary The method of nanosecond time-resolved photothermal displacement spectroscopy in combination with time-resolved light reflectivity measurements has been used to study aluminum and stainless steel substrates with sputter deposited Au and Sn films. The results show, that this method can be used as a non-contacting surface thermometer. In addition, a strong correlation between signal decay and film thickness could be observed.

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Untersuchung transienter thermischer Oberflächenprozesse

     

Struktur und reaktivität des koordinativ überladenen komplexes dichloro-η5 -cyclopentadienyl- tris(tetrahydrofuran)ytterbium(III)

The crystal and molecular structure of (η⁵ -C₅H₅)YbCl₂(THF)₃ (1), which crystallizes e.g. from solutions of [(C₅H₅)₂YbCl]₂ in THF, fully corresponds to the structure of the previously examined Er-homologue. In accordance with its rather high SAS-value (0.784), 1 loses spontaneously two THF ligands when exposed to toluene.     

Unusual selectivities of radical reactions. Experimental studies on alkyl versus phenoxyl reaction systems

Radical reactions involving two or more intermediates and many mutual reaction channels may lead to the specific formation of one cross-reaction product if one species is rather persistent and if transient and persistent species are produced with equal rates. A previous kinetic analysis of the phenomenon revealed that the concentrations of the intermediates and the selectivities of product formation depend critically on the relative initiation rates. The present experimental ESR studies on systems involving simultaneously generated phenoxyl radicals as persistent and alkyl radicals as transient species confirm the predicted behavior. They also lead to absolute rate constants for reactions of alkyl with phenoxyl radicals and for hydrogen atom transfer from phenols to alkyl radicals.