Visible-light detoxification and charge generation by transition metal chloride modified titania

Amorphous microporous metal oxides of titanium (AMM-Ti) modified with chlorides of PtIV, IrIV, RhIII, AuIII, PdII, CoII, and NiII have been prepared by the sol-gel method and characterized by various surface analytical methods. These hybrid AMM-Ti powders are catalysts for the photodegradation of 4-chlorophenol (4-CP) in aqueous solution when illuminated with visible (lambda > or = 400 or 455 nm) or UV (lambda > or = 335 nm) light. The initial rate depends on the dopant level and is highest at 3.0% Pt in the case of PtIV/AMM-Ti. When employed in a photoelectrochemical cell, the activity spectrum of the photocurrent extends downward to about 600 nm, as does the photodegradation of 4-CP. It is suggested that the metal salt acts as a redox-active chromophore, transmitting the photogenerated charges to the amorphous matrix.     

Certified reference materials for the quality control of measurements in environmental monitoring

The monitoring and protection of the environment are based on measurement campaigns which cover long periods of time and large geographical areas. Only accurate analytical results allow valid conclusions to be drawn about a situation and its evolution. The use of certified reference materials (CRMS) permits verification of the accuracy of the measurements. The importance of accuracy and the way CRMs may be used are presented in this review. The production and properties required of a good CRM are discussed. An overview of the types of CRMs in the non-nuclear field, available for the monitoring of the environment, is also given.     

Spectroscopic Characterization of Open-Shell Cations: Emission and Laser Excitation spectra of Rotationally Cooled CH3(CC)2X+, X = Cl,Br

Gas phase emission and laser excitation spectra of the òE?X?²E (Σ = +½, ?½) transition of rotationally/vibrationally cooled 1-chloro- and 1-bromo-1,3-pentadiyne cations have been obtained. The emission was excited by electron impact on a seeded helium supersonic free jet and the fluorescence by laser excitation of cations produced by Penning ionization and collisional relaxation. From these two sets of data the origin bands of the spin-orbit systems are located and for the bromo species this leads to better values of the spin-orbit splitttings in the two electronic states and of the first adiabatic ionization energy. The vibrational frequencies of many of the fundamentals of these cations in the X?²E and òE states have been obtained to within ±2 cm^?1.     

On existentially closed and generic nilpotent groups

Letn≧2 be an integer. We prove the following results that are known in casen=2: The upper and the lower central series of an existentially closed nilpotent group of classn coincide. A finitely generic nilpotent group of classn is periodic and the center of a finitely generic torsion-free nilpotent group of classn is isomorphic toQ ⁺, whereas infinitely generic nilpotent groups do not enjoy these properties. We determine the structure of the torsion subgroup of existentially closed nilpotent groups of class 2. Finally we give an algebraic proof that there exist 2^κ non-isomorphic existentially closed nilpotent groups of classn in cardinalityK ≧N ₀. Some results of this paper were contained in [6].     

Produkttreue Klassen universeller Algebren

Ohne Zusammenfassung     

Two-Photon Raman scattering and high excitation luminescence in ZnTe

Two-Photon-Raman Scattering (TPRS) and the luminescence of ZnTe are investigated when the samples are highly excited with a tunable narrow-band dye-laser. In luminescence, one observes emission bands due to the well-known inelastic exciton-exciton scattering at intermediate excitation intensities, and the recombination radiation of an electronhole plasma (EHP) at the highest excitation levels. For the first time, TPRS is reported in ZnTe. From the change in the TPRS lines in magnetic fields up to 10T we deduce a diamagnetic shift of 1.2°10^?2 meV/T² of the free longitudinal exciton. This value is in good agreement with results obtained by other authors from reflection spectroscopy.