Präparation und Supraleitungseigenschaften von Zweikomponenten-Diffusionsschichten auf Niob und Vanadium

Earlier experimental work on one-component diffusion of tin into niobium wire or of silicon into vanadium wire has been carried out to prepare diffusion-layers with high-field superconductive characteristics. As a continuation of these investigations, layers have been prepared on niobium and vanadium wire by simultaneous two-component diffusion out of the vapour phase. Here tin or silicon acts as one of the components diffusing into niobium or vanadium respectively, whilst the second component in each case consists of elements chosen from neighbouring regions of the Periodic System. In most cases the introduction of the second component into the diffusion layers results in a decrease of the transition temperature observed for one-component diffusion. It is most probable that this decrease is caused by the high vapour pressure of the second component compared with that of the first, tin or silicon. This would result in diffusion-layers having a greater concentration of the second component. However, it is also to be expected that the rate of diffusion ratio of the two components, which is strongly temperature-dependent, has an important effect on the constitution of the diffusion-layers.     

Einfluß von Temperatur und Druck auf Kristallfeld und Elektronenterme in EuZn-Nitrat

Zeitschrift für Physik A Hadrons and nuclei - Die Verschiebung der Absorptionslinien von monoklinem EuZn-Nitrat in Abhängigkeit von Temperatur und allseitigem äußerem Druck wird...     

Die erste Arbeitskonferenz über Frequenznormale und Deren Standardisierung,Frequenz- und Impulsuntersetzer

Ohne Zusammenfassung     

Bitter-Streifen und Bloch-Wände

Through simultaneous use of the magneto-optic and powder-pattern methods, observations leading to a number of unexpected results were made on the magnetic domains of transformer steel. For example, the colloid lines on the so called stress pattern appear to be located not on the edges of the domains as previously supposed, but in the centers. Through analysis of this and other observations, one must infer that Bitter patterns are not caused by the stray fields of Bloch walls as is usually assumed but predominantly rather by magnetic surface charges on the domains.     

Thermolumineszenz von KCl und NaCl nach Röntgen- und UV-Bestrahlung bei Heliumtemperatur

Glow curves of luminescence are recorded in the range from 10° K to 300° K. One gets characteristic changes by prior annealing the single crystals in O₂ or HCl. Also an increase of the lattice disorder causes new glow bands. In KCl a strong glow band always appears at 40° K after irradiating with X-rays or ultraviolet light in the range of the exciton bands. It is ascribed to trapped excitons, which become mobile at that temperature. For X-ray irradiated KCl the glow curve of luminescence is compared with the electrical glow bands and with the concentration change of known defects. The half widthΔT of all glow bands is found proportional to the temperature of the maximum:ΔT=(0.08±0.02)T _m .     

Temperaturabhängigkeit von Knight-shift und Suszeptibilität von Vanadium und Niob

Knight-shiftK and susceptibility have been investigated on single-crystals of vanadium and niobium between 4 K and 290 K.In the case ofV the changes ofK and are found to be of opposite sign and proportional toT ² with good approximation. This can be explained by theT-dependence of spin-paramagnetism of 3d-electrons. The hyperfine field due to oned-electron spin is found to be — 90 kG. Small deviations from theT ²-law are explained by minor changes in the orbital susceptibility, which gives the main constituents toK and. In the case of Nb only is found to be proportional toT ². TheT-dependence ofK is very small and shows a maximum at 140 K. This can be explained by theT-dependence of spinparamagnetism of 4d-electrons as well as 5s-electrons.     

Eigenschaften und Parameterabhängigkeit der Temperaturverteilung und der Charakteristik eines zylindersymmetrischen Stickstoffbogens

The purpose of this work is to examine the properties and dependence upon parameters of the temperature distribution, and to ascertain the characteristic of a stationary, cylindersymmetrical nitrogen arc with negligible convection. Proceeding from the local balance of energy (the Elenbaas-Heller differential equation), the article makes known a process designed to determine the axial field strength in the arc discharge tube explicity with the aid of the boundary conditions of the temperature and the material functions. To this end, the differential equation is converted to a nonlinear integral equation. This equation can then, provided that the material functions are known and the parameters — radius of discharge tube, axis temperature, wall temperature — are established, be solved either numerically or graphically by a method analogous with the Picard's method of successive approximations. The numerical results, parameter limitations, and assumptions concerning material functions, enable the graphic and analytical relationship between temperature distribution and characteristic to be ascertained within a predetermined range of parameters. Thus we are enabled to interpret and theoretically record a few empirical beginnings and laws.     

Absorptionsquerschnitte und Transmissionskoeffizienten für Protonen und Neutronen nach dem optischen Modell

T _l -values and absorption cross sections for protons and neutrons are calculated with optical potentials, which have been fitted to experimental scattering data. Values are given forZ=10, 20, 30, 50, 70, 90, and energies between 0.1 und 25 MeV. For protons we used the local optical potential ofPerey and for neutrons the nonlocal optical potential ofPerey andBuck. The results are compared with those of other optical potentials. In addition it is shown, that the spin-orbit-interaction leads toT _{l j} -values which sometimes differ appreciably depending whetherj equalsl+1/2 orl?1/2.     

Saisonale Variation von Deuterium und Sauerstoff-18 in Luftfeuchte und Niederschlag über Antarktika

Abstract D and (18)O distributions were investigated in Antarctic precipitation (falling snow) and in water vapour to study their dependance on season and sampling site. Long-term sampling at the former German Georg Forster Station during 1978-93 and at the Japanese Syowa Station during 1994-97 allow conclusions about the present seasonal isotopic variations in the water inflow to Antarctica. The δD and δ(18)O values of precipitation at these East Antarctic coastal stations were compared with corresponding data from the West Antarctic Georg von Neumayer and Halley stations. The monthly means of these long-term data sets show typical hysteresis-like seasonal patterns of isotopic composition. Significant time lags exist regarding station temperatures, while water vapour δD values do not show such hysteresis patterns. Here, half-yearly and even quarter-yearly time components were found by Fourier analysis. Attempts were made to describe the variation in δD and δ(18)O values of water vapour and precipitation as well as in the resulting deuterium excess by the mixed cloud isotopic model (MCIM) of Ciais and Jouzel.     

Anregung von Volumen- und Oberflächenplasmaschwingungen in Al und Mg durch mittelschnelle Elektronen

Dispersion and scattering cross section of the bulk plasma losses of Al and Mg are compared with plasma theory. The low lying Mg loss shows an asymmetric intensity distribution for non-normally incident electrons and an angular dependence of intensity as expected from the theory of surface losses. In very thin Al films, coupling effects between the two opposite surfaces are found, causing some new properties of the surface losses. Especially a thickness dependent dispersion of the surface loss is measured which is quite different from that of the bulk losses and characteristic for surface excitation.