Messung der Fehlordnungsenergie an abschreckend kondensiertem Kupfer bei tiefer Temperatur

Copper films are produced by quenching condensation on a substrate at low temperature. A stored energy release of 216 cal/mole and a resistivity decrease of 1.8μΩcm are observed during annealing from 20 to 60 °K. In this temperature range the recovery of the films is described by a crystallisation of highly disordered material between small crystallites, which are produced during condensation. About 14 atomic-% of the whole film substance take part in this process. The stored energy-resistivity ratioE/Δ? found is 1.9 cal/g/gm/gWcm in the whole temperature range from 20 to 60 °K. This value is in good agreement with the stored energy measurements on neutron-bombarded copper.     

Messung der spezifischen Wärme von abschreckend kondensierten Indium-, Blei- und Wismut-Schichten bei tiefer Temperatur

Thin metal films are evaporated onto a cooled Be-foil at 25–32 °K in high vacuum. After condensation the films have a large degree of disorder. The specific heat is measured in the temperature range from 5–8 °K after condensation and after annealing. No differences in the specific heat are found for disordered and annealed In- and Pb-films. The specific heat of amorphous Bi-films, however, is 1.7 times larger than that of crystalline films. The results are discussed together with investigations of disordered films by superconducting tunneling.     

Messung der Elektronenbeugungsintensitäten polykristalliner Aluminiumschichten bei tiefer Temperatur und Vergleich mit der dynamischen Theorie

By means of a retarding field apparatus the electron diffraction intensities of a polycrystalline Aluminium-foil have been measured for different electron energies between 17 and 50 kev. The specimen was kept at 154 °K and the thickness of the crystallites was about 280 Å. It has been shown that the high index reflections behave kinematically, while the first order reflections [e.g. (111), (200)] are much influenced by dynamical extinction effects which can be explained very well by the dynamical two beam approximation. Also the intensities of the higher orders [e.g. (222), (400)] of the strong reflections show marked deviations from the kinematical values. This intensity deficit can be interpreted by multiple scattering processes due to systematic interactions. The experimental results are compared with the second Bethe approximation (introduction of dynamic potentials) as well as with the second Born approximation where double scattering processes within the crystal are taken into account.     

Hochfrequenzwiderstand abschreckend kondensierter supraleitender Metallschichten

A microwave cryostat is described, which enables us to measure the surface resistance of superconducting films in metastable states. In metastable disordered films often elevated transition temperatures are found. Surface resistance measurements can give information about electronic parameters of such films. In connection withdc-conductivity and critical magnetic field measurements, the mean free path, the penetration depth and the coherence length were determined in the metastable and the annealed state. These values have been compared with those expected from a free electron model.     

Szintillationslichtausbeute von abschreckend kondensierten Anthrazenaufdampfschichten

Thin films of anthracene were produced by evaporation on substrates cooled by liquid air. Fluorescence spectra and X-ray diffraction diagrams indicate a new crystalline phase of anthracene. With increasing temperature this modification shows an irreversible transition into normal polycrystalline anthracene. The scintillation light yield produced by α-particles and electrons is strongly reduced as compared to normal anthracene.     

Messung der spezifischen Wärme und der Fehlordnungsenergie von amorphen Blei-Wismut-Schichten

Amorphous Pb-Films with a 30 atomic-% Bi-content are produced by evaporation onto a cooled Be-foil at 20 °K in high vacuum. The specific heat of these films in the temperature range from 5–8 °K is found to be 1.6 times larger than after crystallization, which takes place during warming up between 30 and 40 °K. The stored energy released during this crystallization amounts to 1.5 kcal/mol.     

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.     

Zur Spinordnung von paramagnetischen Zusätzen in abschreckend kondensierten Schichten aus Supraleitern

The susceptibility of the dilute alloys Pb-Mn, Cu-Mn, Sn-Mn, and La-Gd is measured in the temperature range from 2 to 300 °K. The dilute alloys are produced by simultaneous evaporating of both components on a substrate at 14 °K. In this way one gets a statistic distribution of the paramagnetic impurities in the solvent. The Mn atoms, dissolved in Pb, obeyCurie's law. The paramagnetic Curie temperature equals zero at every chosen concentration for the mentioned systems. Mn in Pb shows an effective magnetic moment of 3.9 Bohr magnetons in the concentration range from 2 to 10 at% Mn. At low temperature there exists a quasi-antiferromagnetic ordering among the spins of the Mn atoms. The temperature at which this ordering appears, linearly increases with the concentration of Mn. With regard to the systems of Cu-Mn, Sn-Mn, and La-Gd we also find an antiferromagnetic spin ordering. The transition temperature of superconductivity is depressed by adding Mn to Pb. The decrease disappears when the Pb-Mn films are annealed to 290 °K. This agrees with the fact that Mn loses its magnetic moment after annealing the films to room temperature.     

Lokale Messung von Driftgeschwindigkeit und Temperatur der Ionen einer Argon-Niederdruckentladung mit resonanter Laserstreuung

The radial ion drift velocity and temperature in an argon low-pressure discharge have been measured by a resonant laser scattering method with high spatial resolution. The detection limit for the drift velocities was 2 · 10⁴ cm · s^?1. In the vicinity of the discharge axis the drift velocity grows linear with the distance from the axis. The measurements have shown the existence of a radial dependence of the ion temperature T¹(r). Comparisons of axial ion temperature T_? with T_‖(r = 0) are an experimental demonstration of the anisotropy of the ion velocity distribution in this kind of discharges.     

Markierungsprobleme bei der Messung von Verweilzeitspektren in Hochdruckhydrieranlagen

Es wird über Untersuchungen des Verweilzeitverhaltens der flüssigen Phase in einer kleintechnichen Hochdruckhydrieranlage berichtet. Die Messungen wurden mit Hilfe des radioaktiven Nuklids ⁸²Br in Form von Methylenbromid (CH₂Br₂) durchgeführt. Untersucht wurde das Verweilzeitverhalten bei verschiedenen Durchsätzen und unterschiedlichen Betriebsweisen der Anlage, wobei Temperaturen gewählt wurden, bei denen keine Hydrierreaktionen ablaufen.     

Die Messung der β-γ-Winkelkorrelation bei Au198

The energy dependence of theβ ?γ asymmetry coefficient has been measured. No anomaly at lowβ energies as reported by other authors was found. Theξ-approximation holds andε W/p ² Ν ₁₂=0.027±0.007 was obtained. The matrix elements of theβ transition are discussed.     

Messung der Winkelverteilung der Neutronenpolarisation bei Streuung von 15,85 MeV-Neutronen am Kohlenstoff

AtE _n=15.85 MeV the angular distributions of neutron polarizationP(θ) for¹²C(n, n)¹²C and of scattering asymmetry A(θ) for¹² C(n,n′)¹² C ^*(Q=?4.43 MeV) have been measured. In a neutron time-of-flight method with a plastic scintillator as scatterer carbon recoil nuclei were used for detection. Polarized neutrons were produced in thed-t reaction atE _d=1.90 MeV at a reaction angle of 70° (lab.). WithP _n=?0.135 scattering polarizations P(θ) are forθ _lab=30, 40, 50, 60, 70, and 80° respectively ?27.0±2.1, ?48.4±2.7, ?68.7±3.6, ?20.7±6.2, +5.3±3.9, and +2.1±4.5%.