The electron affinity of tungsten

The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm^-1 by observing the onset of the process when W^- ions in the 5d⁵6s²5d^56s^2 ⁶S_5/2 ground state are photodetached producing neutral W atoms in the 5d⁴6s²5d^46s^2 ⁵D₀ ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W^-.     

Fundamentals and properties of zinc oxide nanostructures: Optical and sensing applications

In this paper we will give an overview of the status of catalytic growth and of low-temperature chemical growth of ZnO nanostructures performed in our laboratory. Particularly results employing different substrates will be discussed. The second part deals with structural and optical properties of ZnO nanorods. The results from high resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM), photoluminescence (PL), Cathodoluminescence (CL), and Electroluminescence (EL), on single nanowires will be shown. Our results on surface morphology, bulk and the position of the catalyst as well as the optical properties including UV emission, lasing and white emission will all be presented and discussed. In the third part experimental results from electroluminescence of ZnO nanorods on different substrates in the UV in addition to excellent white light emission obtained from samples grown at low temperature are to be given and discussed. Finally the sensing of molecules in water by ZnO nanorods will be discussed from a theoretical point of view. Also fundamental properties of polaritons and excitons in ZnO nanostructures are to be highlighted.     

Excess thermal noise generated during Poiseuille flow of certain polymer solutions

The previously reported results concerning the generation of excess thermal noise induced by capillary flow of aqueous solutions of poly(ethylene oxide) (PEO) are supplemented by measurements on the following solutions: PEO/DMF, PEO/i-PrOH, PS/THF, PVAC/cyclohexanone, and poly(acrylamide)/water. Similarly to the previous findings, a noise level increasing with the flow rate is recorded, the noise exhibiting a l/f -frequency spectrum. Within a certain flow range, distinct peaks are recorded in the spectrum (harmonics of a fundamental frequency,f ₀). Thef ₀-values of the various solutions under varying flow conditions arrange themselves along a commonf ₀-shear rate curve. They appear to be associated with transversal oscillations of the solution upstream the capillary entrance.     

Electrical properties of filled polymers and some examples of their applications

Polymers containing electrically conductive fillers show interesting electrical properties like semiconductors and metals without losing the processability of polymers. Typical applications are as antistatic (electrostatic dissipation) materials, electro-magnetic interference shielding materials, heaters and sensors. The selection of filler and polymer governs the properties obtained in such composites.     

Eine Tabelle zur Bestimmung der Gewichts- und Volum-Prozente des Methylalkohols

Ohne Zusammenfassung     

Growth of ZnO nanostructures by vapor–liquid–solid method

Zinc oxide nanorods have been grown by vapor–liquid–solid (VLS) catalytic growth. The optical properties and structures properties of the grown ZnO nanostructures have been studied by photoluminescence, high resolution X-ray diffraction and scanning electron microscopy. The results show that the formation of ZnO nanostructures is strongly influenced by the growth conditions and used substrates. It was found that oriented ZnO nanorods are grown more easily on a substrate with a similar crystalline structure as ZnO. By optimizing growth conditions, oriented-ZnO nanorods grown on Si(001) substrate with a diameter of around 300 nm and lengths of 20 to 35 μm have been achieved, and they show excellent optical properties. Laser action has been observed at room temperature by using optical pumping. PACS 81.05.Dz; 81.10.Bk; 81.16.Hc     

Selen

Ohne Zusammenfassung     

Aklyl Chain Order Parameters and Phase Diagrams for Systems Containing Sodium n-Octanoate,Water, and Different Alcohols

Lamellar liquid crystalline phases containing sodium n-octanoate, water, and an alcohol have been studied by means of ²H NMR. Order parameters have been determined for the octanoate alkyl chain in systems containing ethanol, 1-propanol, 1-butanol, 1-pentanol, benzyl alcohol or 1, 8-octandiol. The straight chain alcohols yield decreasing octanoate order parameters with decreasing chain length. With 1, 8-octandiol the octanoate order parameters are somewhat smaller than with 1-propanol, indicating quite flexible octanoate hydrocarbon chains. Using mono-deuteriated benzyl alcohol. C₆H₅CHDOH, the S_CD as well as the S_HD (= S_HH ) order parameters were determined in the same measurement. A typical measurement yields |S _HD|-|S_CD | = 0.04 ± 0.04, where the error estimation includes the uncertainties in the quadrupole and the magnetic dipole-dipole coupling constants. It is stressed that in order to ascertain a significant difference between S_HH and S_CD , it is necessary to know the coupling constants with high accuracy. The phase diagram for the system sodium n-octanoate/water/benzyl alcohol was determined, mainly by ²H and ²³Na NMR.