Zur Asymmetrie der Reaktion139La(n,α)136Cs mit polarisierten Neutronen

Experimental and theoretical investigations have been performed to determine the thermal conductivity of hydrogen in the temperature range between 2000 and 7000 °K. For this purpose the radial temperature distributions for various currents and theE-I-characteristic of a low current wall-stabilized hydrogen arc have been measured. In the dark region of the arc outside the bright core the temperature and the thermal conductivity between 2000 and 4500 °K were found by means of the schlieren technique. The electron temperature in the core of the arc results from spectroscopic measurements. The gas temperature has been calculated with a formula, derived from the kinetic theory of gases. Assuming a constant collision integralQ _eH ¹¹ the radial distribution of electric conductivity has been calculated according to Langevin's formula. The valueQ _eH ¹¹ =30·10^?16 cm₂ results by comparing the integrated conductance with the measured one. Since now the radial distribution of power input and the temperatures are known, the thermal conductivity between 4500 and 7000 °K can be determined as well. The total course of the heat conductivity shows a strong peak at the temperature of 3740 °K characteristic for the dissociation process.     

Strippingreaktionen mit polarisierten Deuteronen

The nucleons liberated in a (d, p)- or (d, n)-stripping-reaction are generally polarized even if unpolarized deuterons are used. In this paper however these reactions are examined for polarized deuterons in order to provide more detailed information concerning the interactions between the reaction products.     

Theoretische Aspekte der Untersuchung des Stickstoffmetabolismus mit 15N beim Menschen II. Probleme der Auswertung und Interpretation klinischer Untersuchungen

Klinische Untersuchungen zum menschlichen Stickstoffmetabolismus, die unter Verwendung des stabilen Stickstoffisotops ¹⁵N durchgeführt wurden, werden mit Hilfe eines 3-Compartmentmodells ausgewertet und interpretiert. Möglichkeiten zur Erweiterung dieses Modells werden diskutiert, und durch Computerstudien wird die Aussagekraft der aus Modellen gewonnenen Resultate überprüft.     

Grundlagen der Polarisationsmessung in polarisierten Targets mit Hilfe des inneren Feldes

It is shown how the difficulties with the “Lorentz field” method of Abragamet al. for the measurement of nuclear polarization can be resolved. The observable field shift is derived as a function of nuclear polarization, target shape and some other parameters. For purposes of practical application numerical results are presented for polarized targets of lanthanum magnesium nitrate (1% Nd) having the shape of thin square slabs.     

Untersuchungen zur entstehung der messignale bei der Permalloy-Sonden-methode

Local and short-ranged magnetic fields can be detected by the Permalloy-Sonden method. An extensive knowledge of the origin of the measuring signals is required in order to carry out quantitative measurements with the help of this method. For that purpose, measurements in calculable magnetic fields of two-wire circuits were made. The measurements can be described quantitatively with regard to finite extension of the top of the sonde and the spatial field-strength distribution of the two-wire circuits.     

Abscheidung von Glimmpolymerschichten in einem weiten Metallrezipienten und Untersuchungen zur Struktur

Investigations are reported of growth rate, chemical structure (IR-spectroscopy, mass-spectrometry), thermal stability, surface structure (scanning electron microscopy) of thin polymeric films grown in a gas (Ar-hexamethyldisiloxane-mixture) discharge with a heated cathode, which is situated in the centre of a cylindrical metallic vessel (l = 50 cm, 2r = 30 cm). The discharge conditions are the following: I = 0,25 – 4 A, U = 30 – 100 V, p = 6 – 40 Pa, argon flow rate = 3,8 · 10^?5 mol/min, Ar/HMDS = 1 : 0,7 – 1 : 2,4. The growth rate changes from 2 to 18 nm/min, depending on the discharge conditions. The reproducibility of the growth rate shows deviations smaller than 10%. The films consist of a highly cross linked polymeric material and are stable up to 260°C, the solubility in n-hexane being smaller than 2%. The surface of the thin film (d ～ 10² nm) is smooth. Corrosion resistance to soda lye (0,2% NaOH) has been proved.     

Untersuchungen zur Zeeman-Spektroskopie mit Hilfe nichtlinearer Resonanzen eines Multimoden-Lasers

Intensity dips in the output power of a multimode He/Ne-Laser as a function of an axial magnetic field have been measured up to a field strength of 600 Gauß. These intensity dips are appearing if the Zeeman-splitting is equal to the frequency separation of different modes. The effect is used for Zeeman-spectroscopy. A discussion of the observed phenomena is given based on Lamb's Theorie. The measured value for the Landé-Factor of the 2p ₄ Ne-level isg _j (2p ₄)=1.3005 (±0.2%).     

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.     

Spektroskopie der Protonen aus Kernreaktionen mit 14 MeV-Neutronen mit einem Zählrohrteleskop

Protons from nuclear reactions induced by 14 MeV neutrons are studied by means of a telescope, consisting of three CO₂-flow counters and a surface barrier detector. The resolving power of this arrangement, tested with recoil protons is found to be 400 keV at 14 MeV, the efficiency (counts per incident neutron) being 3 · 10^?7. From the measured energy spectra of the protons from the metals Ti, Fe, Ni and Zn in forward direction statistical theory parameters are evaluated. In the level density expression ρ(E_a)～E _a ^?n exp(2√aE_a) the exponentn=2, including angular momentum effects is found to be in better agreement with the experimental data than othern-values frequently used.     

Absolutbestimmung der austrittsarbeit von palladium mit einem röntgenphotoelektronenspektrometer

Based on the work of Ascarelli and Missoni⁴ and Evans¹ a method for absolute measurements of work-functions of electrically conductive samples is developed which is applicable to instruments without retarding field and with a spherical analyzer. The calibration of the instrument, as well as the determination of the onset of the secondary electron spectrum and the Fermi-level, are discussed. For a polycrystalline palladium platelet with an argon-ion cleaned surface, a work-function ofW′_Pd = 4.5(4) ± 0.2(0) eV has been obtained, which agrees with the literature value³ of 4.64 eV within the range of accuracy.     

Physikalische Probleme der Untersuchungen zur Kernfusion in Kondensierter Materie

An avalanche-like increase of research activities in the field was caused by the spectacular announcements and publications about the observation of nuclear fusion processes during the infusion of deuterium into metals. Though, the original claims by Fleischmann and Pons concerning the observation of macroscopic amounts of heat so far seem not to be approved in a quantitative manner by other groups, there are indications for the start of a new interesting field of research at the border between nuclear physics and solid state physics – investigations of nuclear fusion processes in condernsed matter. First conclusions drawn here about possible mechanisms of such processes have to be considered neither complete nor final.     

Autoradiographische Untersuchungen der Stromverteilung auf Platten von Bleiakkumulatoren mit Hilfe der Mikrotomie

Bisherige Untersuchungen der Stromverteilung auf Bleiakkumulatorplatten mit Hilfe der Autoradiographie beschränken sich auf die Anfertigung von Oberflāchen-Autoradiogrammen und Dünnschnitten der Platten quer zur Plattenoberfläche und deren Auswertung. Durch Modifikation eines Verfahrens zur Herstellung von Dünnschnitten der Platten mit Hilfe eines Mikrotoms konnten Schnilte parallel zur Plattenoberfläche erhalten werden. Die Stromverteilung ūber die Plattendicke wurde in Abhängigkeit von der Schwefelsäuredichte und der Entladeslromstärke ermittelt. Außierdem wurden geladene Platten geschnitten und untersucht. Die Ermittlung der Stromverteilung erfolgte qualitativ durch die Herstellung von Avtoradiogrammen und quantititativ durch Aufnahme von Impulsdichte-Zeit-Kurven mit Hilfe eines Scanners.