Studium der van der Waals-Kraft im Bereich kleiner Abstände

The theory of Dzyaloshinskii allows us to calculate the van der Waals force acting between two surfaces which are held at a distance of 10⁴ Å and less. This calculation was based on the experimentally determined absorption data of quarz. The deflection of a thin quarz plate which was supported at one end with a vaporized bar has been measured to verify the theoretical results. Within the range of accuracy a fair agreement could be reached.     

Anomale Anisotropie der zwischenmolekularen Kraft

In addition to previous measurements of anisotropy factors of intermolecular force by atomic beam scattering of Ga by He, Ar, and Xe, a similar determination has been carried out for Ga and Ne. This anisotropy is reversed in sign, presumably reflecting strong influence of repulsive potential term.     

Anisotropie der Plasmaschwingungen in Graphit

Energy loss spectra of electrons at different incidence angles α against the crystal axis were measured in transmission of thin graphite single crystals. The spectra show that the energy and the intensity of the loss peaks are dependent on the angle between the transferred pulse?k _p and the crystal axisc.     

Anisotropie der elektrischen Leitfähigkeit in diglycinselenat-einkristallen

The d.c. electrical conductivity of very pure diglycine selenate single crystals has been studied in the temperature range of 20–110°C. The samples were grown from a solution. The measurements were performed at an applied electric field below 50 V/cm and the results show an anisotropic behaviour of the conductivity in this organic crystal. A dependence of the activation energy on the direction of the applied field is shown. Crystallographic and dielectric constant data are also included in this report.     

Messung der Asymmetrie der Bremsstrahlung transversal polarisierter Elektronen

The asymmetry of Bremsstrahlung emitted from transversely polarized electrons is measured for monoenergetic electrons of 300 keV at an emission angleΘ=22±20°. The experiment yields an asymmetryS=?(0.133±0.020)·αZ for a quantum energy of 60 to 240 keV. Exact calculations for the electron-energy used do not exist. The result is not in agreement with calculations in Born approximation. The apparatus is described, the results with all corrections are discussed.     

Optische Messung der Hyperfeinstrukturaufspaltungen von CoI-Termen

The spectrum of⁵⁹CoI has been investigated by a direct optical method. The hyperfine-splitting of 61 lines between 3,412 and 6,082 Å has been determined. A special numerical technique has been used to decompose the unresolved profiles. For 36 niveaus theA-factors and from these the magnetic field strength at the nucleus have been obtained and also someB-factors. The accuracy of theA-factors lies between 0.5 and 5 percent.     

Messung der lichtelektrischen Leitung in Anthrazenkristallen

The drift mobility of holes in pure Anthracene has been measured by the transient photoconductivity technique used byKepler andLeblanc. The mobility is 0.8 cm²/Vsec and varies asT ^?2. In Tetracene-doped crystals the drift-mobility of holes decreases with growing Tetracene concentration and it varies exponentially as-T ^?1, which suggests that Tetracene acts as a trap. The trap depth is 0.45 eV. By pre-irradiation with α-particles or X-rays the photocurrent is reduced and it is supposed that α-irradiation produces deep traps, whereas X-rays produce as well shallow as deep traps.     

Messung der Paarkonversionskoeffizienten von59Co

Internal pair formation propabilities in⁶⁰Ni and⁵⁹Co have been determined by a positron annihilation method. The electrons from the β^?-decay of⁵⁹Fe were measured in triple coincidence with annihilation quanta originating from pairs produced in the deexcitation of the⁵⁹Co nucleus. By this triple coincidence technique it was possible to measure separately the pair formation coefficients Γ for transitions in⁵⁹Co. The observed values Γ_1.29=(3.7±0.4)×10^?5 and Γ_1.10=(0.5±0.1)×10^?5 are in agreement with theoretical calculations forE2-radiation.     

Messung der Magnetostriktionskonstanten des Kobalts als Funktion der Temperatur

The single crystal magnetostriction constants of hexagonal cobalt are measured between ?200 °C and 400 °C in magnetic fields up to 26 kOe. The shear constant λ_E=2 λ_D?λ_A/2?λ_C/2 which is of interest in connection with domain structures, as well as the volume constant λ_V=λ_A+ λ_B+ λ_C show a relatively strong temperature dependance, which cannot be explained by present theories.     

van der Waals revisited

The van-der-Waals version of the second virial coefficient is not far from being exact if the model parameters are appropriately chosen. It is shown how the van-der-Waals resemblance originates from the interplay of thermal averaging and superposition of scattering phase shift contributions. The derivation of the two parameters from the quantum virial coefficient reveals a fermion-boson symmetry in non-ideal quantum gases. Numerical details are worked out for the Helium quantum gases.