Elektrometrie

Ohne Zusammenfassung     

Raman study of gallium chlorosulphides in chloride melts

The reaction between sulphur and gallium in chlorobasic melts at ca. 500°C was studied by visual observation and by Raman spectroscopy. The results suggest the formation of charged long chains (-GaCl₂-S-GaCl₂-S-) in these melts and the presence of the radical anion S₃^? under certain conditions.     

Local Observation of Field Polarity Dependent Flux Pinning by Magnetic Dipoles

A scanning Hall probe microscope is used to study flux pinning in a thin superconducting Pb film covering a square array of single-domain Co dots with in-plane magnetization. We show that single flux quanta of opposite sign thread the superconducting film below T(c) at the opposite poles of these dipoles. Depending on the polarity of the applied field, flux lines are attracted to a specific pole of the dipoles, due to the direct interaction with the vortexlike structures induced by the local stray field.     

111Cd TDPAC investigation of metal sites in superoxide dismutase: A comparison with X-ray diffraction data

¹¹¹Cd Time Differential Ferturbed γ-γ Angular Correlation (TDPAC) has been used to investigate the Zn-site in Cu₂, Zn₂-superoxide dismutase. These experiments show a clear difference between Cu(II)₂ Cd₂ SOD and Cu(I)₂Cd₂SOD. The result of Cu(II)₂, Cd₂-SOD agrees with the Angular Overlap Model (AOM) applied to the known crystal structure using known partial field gradients for the ligands involved, whereas the results from the experiments with Cu(I) show that a significant conformational change must have taken place at the Zn-site. A proposal for this conformational change has been achieved by computer-modelling.     

Raman study of halogen exchange equilibria in low melting mixtures consisting of sodium tetrachloroaluminate and tetrabromoaluminate

The halogen-redistribution reactions between [AlCl₄]^? and [AlBr₄]^? in molten mixtures of NaAlCl₄ and NaAlBr₄ with widely varying mole ratios have been studied by Raman spectroscopy at 160–300°C and the melting points have been measured. By monitoring the intensities of the totally symmetric stretching a₁-modes of both the parent tetrahalides as well as those of the mixed halides [AlCl₃Br]^?, [AlCl₂Br]^? and [AlClBr₃]^? it is concluded that the mixtures equilibrate very fast and consist of an almost random distribution of the five species. NaAlCl₄ and NaAlBr₄ form an eutectic mixture with a molar ratio near to 4:1, with a melting point of ca 142°C.