Band 20, Heft 4

A brief consideration of the problem of gravitational waves is given on the basis of the following assumption: The components of the metric tensor are functionals of a field by which, in the sense of HEISENBERG’S nonlinear theory, all other fields resp. the corresponding interactions can be deduced. For the sake of mathematical simplicity a scalar field Φ (noncharged bosons) is considered instead of a spinor field. The condition g mn =g mn (Φ) resp. R mn = R mn (Φ) leads to the statement that the concept of a free gravitational wave, i. e. a wave which is a solution of R mn =0 or R klmn = 0, cannot be accepted. A free wave is here by definition a wave which is so far from the origin that one can neglect in the field eqs. all terms which represent a strong interaction. A comparison with a spinor field leads, with regard to this definition, to the conclusion that a free wave may be considered as a neutrino wave and gravitation as the weakest interaction possible of neutrino fields.

The graph scheme developed in 1 is further investigated. The structure of the coefficients α k is determined in terms of α 0 and the projections of the splitting graphs. This allows a formal summation of the k-series. The first few terms of the strong coupling series for the lowest mass eigenvalue are computed for the λ φ 4 theory. The leading term for large λ is complex. This restricts physically acceptable solutions to λ below some critical value. By including a bare mass m in the Lagrangian. the α k become dependent on it. Consideration of one α k e. g. α 0 (m, λ) should then be sufficient for the determination of physical mass eigenvalues.

Die Temperaturabhängigkeit des elektrischen Widerstandes wird untersucht, wobei auf die Näherung freier Elektronen verzichtet wird. Die hierzu benötigten Kenntnisse über die Elektronenstruktur werden mit der Pseudopotentialmethode gewonnen. Außerdem wird die von BARDEEN und PINES entwickelte Behandlung der Elektron-Phonon-Wechselwirkung für den Fall nichtfreier Elektronen verallgemeinert. Das für die Streuung der Elektronen maßgebende Spektrum der Gitterschwingungen wird gitterdynamisch bestimmt. Wenn Austausch- und Korrelationseffekte berücksichtigt werden, findet man ausgezeichnete Übereinstimmung mit dem experimentellen Temperaturverlauf des elektrischen Widerstandes. Ihre Vernachlässigung gibt einen um den Faktor 1,5 - 2 zu kleinen Widerstand.

Starting from COHEN’S theory of square cascades and countercurrent separation processes, column constants for the three types of thermal diffusion columns are calculated. It is assumed that the transport coefficients may be regarded as constants, whereas their values are taken at the mean temperature in the column. By comparison with other theories and experimental results our simplified theory appears to be as good as the more refined ones.

It is shown that in α-copper-aluminium alloys interstitials are able to change sites with the copper and aluminium atoms by diffusion. The activation energy for migration of interstitials could be determined to be 0.82 eV. In a well annealed specimen the interstitials and vacancies annihilate nearly exclusively by pair recombination. The production rate of free interstitials is found to be slightly larger than that of free vacancies during an irradiation with fast neutrons. The excess interstitials, which are supposed to originate from depleted zones, form clusters acting as sinks, at which essentially interstitials anneal out. Due to these sinks another steady state equilibrium („fixed vacancy case“) among point defects and sinks is achieved by repeated irradiations.

The 36 Cl produced by spallation reactions and neutron capture on 35 Cl has been measured separately in three stone meteorites and one iron meteorite. The spallation produced 36 Cl activities - given in dpm per kg (Fe+Ni + 10 x Ca) -have been found to be (20.5 ±2) for Abee - Centre, (21.8 ±2) for Abee - Surface, (21.3 -26.2) for Leedey, and ≦ (22 ±10) for Norton County- Surface. They are in good agreement with those found in iron meteorites of comparable size and known terrestrial age. The neutron induced activities in the same samples are (0.21 ±0.2), (0.08 ± 0.17), (1.7 ±1), and ≦ (30 ± 15) dpm/100 mg Cl. In spite of the large uncertainties highly significant conclusions can be drawn from these data regarding the mass loss of the meteorites during approximately the last million years, either by space erosion or due to ablation during the passage through the terrestrial atmosphere. Based on calculations of EBERHARDT, GEISS, and LUTZ the ratio of post-atmospheric to pre-atmospheric radius derived for the three meteorites is Abee: r M /R=0.86 or r Μ /R > 0.7 on the 3 σ significance level, Leedey (meteorite shower): r M /R=0.5, and Norton County: r M /R=0.77 or r M /R > 0.63 (3 σ level). No neutron induced activity could be detected in the iron meteorite Cranbourne (Nr. 4). The total and spallation produced 36 Cl of two adjacent samples - although differing in their Cl content by more than a factor of twenty-was the same within the experimental limits of error (4.7 ± 0.2) dpm/kg. The low value is attributed to a high terrestrial age and/or the size of this meteorite. 39 Ar could not be detected (< 0.64 dpm/kg. 3 σ level).

The alpha activity of natural neodymium and enriched Nd 144 and Nd 145 was studied with gridded ionization chambers. The alpha energy of Nd 144 was found to be (1.83 ± 0.02) MeV and its half-life (2.1 ± 0.4) · 10 15 years. The alpha half-life of Nd 145 was found to be longer than 6·10 16 years.

The laser mechanism in a p-type GaAs slab with no junction and a hole concentration higher than 7 x 10 18 cm -3 is investigated theoretically for the case that the excited electrons are injected from a gas discharge outside the slab. With such an excitation by slow electrons a lower bound of the current density is calculated from the Schawlow-Townes condition. The losses of diffraction and absorption mechanisms are taken into account. Since the slab can be very thin, minimum current densities with laser action of 10 amp./cm 2 are possible. Several absorption and excitation mechanisms are discussed. Their relative importance may be found from the spectrum of the laser light and the depth of the activation zone of the slab.

Bei absorbierten Dosen größer als etwa 10 6 r (Bestrahlung mit Co 60 ) zeigen sich Veränderungen im elektrischen Verhalten von Mikroplasmen (MP). Die MP-Impulse treten nicht mehr statistisch auf, sondern in Paketen („Nachzünden“). Es wird gezeigt, daß sich aus der Nachzündhäufigkeit je Impulspaket die energetische Lage der strahlungsinduzierten Haftstellen bestimmen läßt. Mit Hilfe der SHOCKLEY-READ-Theorie wurde eine Beziehung abgeleitet, wonach die Nachzündrate eine Funktion der Dichte der Haftstellen, ihrer energetischen Lage und einiger elektrischer Parameter des MP ist. Diese Beziehung konnte durch einige Messungen experimentell bestätigt werden.

Rare earth-mono-terpyridyl complexes of the type M (Terp) Cl 3 · n H 2 O (M = Ce- Gd, Terp = terpyridyl and n = 1- 2.5) have been prepared and their ultraviolet, visible and infrared spectra have been investigated. Probable assignments of the excited levels of the tripositive rare earths to the observed bands are given. The f → f transitions of the rare earths show red shift in the methanolic solution of the chelates with respect to the aquo ions. Definite indications of 4f → 5d transition of the Ce (III) and electron transfer band from the highest filled M.O. of the ligand to the partly filled 4f shell of Eu (III) and possibility of the same in case of Pr (III), Nd (III) and Sm(III) have been obtained. The infrared studies of the solid chelates strongly suggest the coordinated nature of the terpyridyl molecule. Some infrared bands of the chelates show shift towards higher wavenumber and lowering of intensities compared to the free ligand. Of particular interest is the pyridine ring breathing vibration of terpyridyl at 988 cm -1 which shows a shift of ~ 25 cm -1 in the chelates. The out-of-plane inphase C -H deformation band at 830 cm -1 of terpyridyl shows considerable decrease of intensity in the chelates.

Binary molten systems of TlCl. TlBr and TlJ mixed with alkali nitrates have been studied. The existence of miscibility gaps in the liquid state for the seven different systems NaNO 3 + Tl (Br, J). KNO 3 + Tl (Br, J), RbNO 3 + Tl (Br, J) and CsNO 3 + TlJ has been pointed out. The ability to demixing according to some characteristics of the couples of cations in each system has been discussed.

Molten silver-tin alloys have been studied by x-ray diffraction technique, using a focusing Θ--Θ diffractometer with Mo-Ka radiation (quartz crystal monochromator in the diffracted beam). The scattered intensities I coh eu in electron units and the interference function I (K)=I coh eu /ƒ 2 being the scattering factor) have been measured in the range of K=4 π sin Θ/λ = 1.4 Å -1 to K = 15 Å~ -1 for 6 different alloy compositions at temperatures 100 °C above the liquidus line. Four alloys (from 62% to 82% Ag) were measured at 825 ℃ . The positions of the first maximum of I eu or I(K) shift considerably with increasing silver content from K=2.25 Å -1 for pure Sn to K=2.64 Å -1 for pure Ag. The radial distribution function 4 π r 2 ϱ (r) and the probability function W (r) = ϱ (r)/ϱ 0 , where ϱ (r) and ϱ 0 are the atomic and average atomic densities respectively, were obtained by FOURIER transform of I(K). The positions of the first maximum of 4 π r 2 ϱ (r), (i. e., r 1 ) and of W(r), (i.e., r 1 1 ) are a measure of the interatomic distances, and vary from r 1 1 = 3.18 Å for Sn to r 1 1 = 2.86 Å for Ag. The plot of r 1 1 vs. composition of the alloys shows a negative deviation from a linear law. A discontinuity appears in the curve in the range of 50-60% Ag. The coordination number Z increases rapidly on addition of Ag to Sn (Z = 8.5 for Sn) and reaches a value of about 11 beyond 60% Ag.

The proton magnetic resonance spectrum of benzene oriented in a nematic solution is calculated using group theoretical methods. The calculations agree within experimental errors with the spectrum of benzene observed in a nematic solution of 4.4′-di-n-hexyloxy-azoxy-benzene. By an improvement of the temperature homogenity in the sample it was possible to obtain linewidths of only about 5 cps for all lines independent of the splitting. It is confirmed that the signs of the scalar coupling constants between ortho and meta protonpairs are positive. A small temperature dependence of the chemical shift of the benzene protons was found in the nematic solution. It is due to the dependence of the average orientation on the temperature.

Bei fünf Wellenlängen im Bereich von 60 cm bis 7 mm wird in benzolischer Lösung bei 20°C die dielektrische Absorption einer großen Anzahl von Benzolderivaten bestimmt. Substituenten sind die polaren Gruppen CHO, COCH 3 · COOCH 3 , OCH 3 , OH, NH 2 , N(CH 3 ) 2 und CH 2 Cl bzw. CH 3 Br. An einfach substituierten Benzolderivaten wird die Momentkomponente senkrecht zur Achse zwischen Gruppe und Benzolring verglichen mit der Komponente, die sich mit besonders kurzer Relaxationszeit orientiert - etwa durch Drehung der Gruppe allein. Es ergibt sich ein qualitativer Zusammenhang zwischen den dielektrischen Relaxationserscheinungen und dem mesomeren Bindungszustand der Substituenten, in den sich nur die Amino- und die Dimethylaminogruppe nicht einordnen. Auch systematische Untersuchungen an zweifach substituierten Benzolderivaten weisen auf eine solche Beziehung hin; in o-Verbindungen ist dabei die sterische Beeinflussung der beiden Gruppen zu berücksichtigen. Letztere kann gegenüber den Monoderivaten zu einer Vergrößerung (Acetylgruppe) oder zu einer Herabsetzung (Methoxygruppe) des beweglichen Gruppenmoments führen.

Bei höheren Temperaturen mißt man für organische Lösungen eine Aktivierungsenergie E 1 der Gleichstromleitfähigkeit, die charakteristisch für den gelösten Stoff ist. Es wird festgestellt, daß eine Substitution am Benzolring von Nitrobenzol und Pyridin eine Erhöhung von E 1 zur Folge hat. Der Effekt kann nicht durch eine Substituenten-bedingte Ladungsverschiebung innerhalb des Moleküls erklärt werden. Dagegen zeigt eine Abschätzung, daß die zusätzliche Aktivierungsenergie betragsmäßig genau mit der zusätzlichen potentiellen Energie übereinstimmt, die ein abzulösendes Elektron im Feld des Substituenten-Dipols besitzt. Dieser Befund bestätigt das früher aufgestellte Modell der Ladungsträgererzeugung, das als Ort der Elektronenablösung die Sauerstoffatome der NO 2 -Gruppe bei Nitrobenzolen bzw. das Stickstoffatom bei Azaverbindungen postuliert.

The photolysis of cyclohexane at 1.0. 0.5, and 0.2 mm pressure and room temperature with an unfiltered hydrogen lamp led to hydrogen, acetylene, ethylene, propene. 1.3-butadiene and cyclohexene as the major products, and other minor products. A consideration of the stoichiometry, the effect of increasing pressure, the dependence on time, and the energetic requirements, suggest that only four processes are important which may arise from an excited state of the cyclohexane molecule. These are (1) (C 6 H 12 )*→C 6 H 10 + H 2 ; (2) (C 6 H 12 )*→-C 4 H 6 + C 2 H 4 + H 2 ; (3) (C 6 H 12 )*2 C 3 H e 6: (4) (C 0 H 11 )*→3 C 2 H 4 . The formation of acetylene is considered to be a secondary process.

A microwave bridge, similar to the optical JAMIN interferometer, has been developed in order to determine the electron density in weakly ionized decaying plasmas. The discharge vessel was located in the open space between two horn antennas. A rather homogeneous excitation was accomplished by using an electrodeless high frequency (f = 13,6 MHz) discharge. Contrary to the common practice of using phase displacements several times of π, only very small displacements of the signal phase, traversing the plasma, have been used. The dimensions of the discharge vessel and the frequency of the microwave (f = 23 GHz; λ = 1,3 cm) have been properly chosen in order to have proportionality between the mean electron density and the oscilloscope trace. The range of electron-density investigated was about 10 8 to 10 10 cm -3 . The operation of the bridge has been investigated during the afterglow of a decaying nitrogen plasma. Simultaneous optical observations have shown that the intensity of the first negative bands of N 2 + (B 2 Σ u + -Χ 2 Σ g + ) is nearly proportional to the electron density. Using this correlation, the electron density profile across the discharge vessel has been evaluated. It could be shown that the time dependance of the electron density in the afterglow changes strongly within the discharge vessel. A comparison between the measurements of the electron density and the optical observations has shown that the microwave bridge is able to give some details of the electron density profile across the discharge vessel, inspite of the large wavelength used, compared with the dimensions of the discharge vessel.

Es wird experimentell gezeigt, daß sich der inverse Pinch wegen seiner Symmetrieeigenschaften sehr gut dazu eignet, zylindrische Stoßwellen zu erzeugen, deren Leuchtfronten wohldefiniert und reproduzierbar sind. Zur Messung der Leuchtfront dienen eine KERR-Zellenkamera und ein Lichtleitersystem, während zur Untersuchung der Stoßfront selbst eine piezoelektrische Drucksonde verwendet wird. Die experimentellen Ergebnisse zeigen, daß Leuchtfront und Stoßwelle übereinstimmen und daß die Ausbreitung der Stoßwelle gut mit Hilfe des Schneepflugmodells beschrieben werden kann.

For the extreme ultraviolet (λ < 1000 Å) a light source has been developed using the lateral emission from a condensed capillary discharge. In that way damages of the spectrometer entranceslit or grating are prevented. The periodic discharges of a condensor through a low-inductance circuit were switched by a rotary spark-gap, which makes possible a control circuit for photon flux stabilization. The light source is rugged, suitable for continuous load, and has a long life time. The effect on emission of the following parameters has been investigated: pressure, repetition frequency, condenser voltage, capacity, discharge energy, and inductance. The dependence of intensity on pressure, voltage, and inductance permits conclusions on ionization stages. The light source can be operated with all noble gases as well as nitrogen or oxygen, giving reproducible many-line spectra with high constancy, among which the spectra of higher ionization stages are predominant. Except the lines of oxygen, originating on the capillary material, no extraneous lines were observed. The spectra of the different gases have been examined in more detail within the region between 350 Å and 945 A. These contain many new lines of argon, krypton, and xenon. It has been shown by other investigations, that the light source emits an intense and copious line spectrum at shorter wavelengths, too, reaching down lower than 100 A.

A redetermination of the isotopic composition of atmospheric neon gave abundance ratios 20 Ne/ 22 Ne = 9.80 ± 0.08 and 20 Ne/ 21 Ne = 338.0 ± 2 .5 , corresponding to percentage abundances of 90.50 ± 0.07 , 0.268 ±0.002 and 9.23 ±0.07 for 20 Ne, 21 Ne and 22 Ne, respectively. These abundances correspond to an atomic weight of 20.179 ± 0.002 for atmospheric neon.

A gravimetric method has been used to study interdiffusion in binary mixtures of AgNO 3 and KNO 3 over the range 50 -75 mole % AgNO 3 at tem peratures below 200°C. The obtained cation diffusion coefficients are of the order of 2 × 10 -6 cm 2 sec -1 i.e. considerably lower than what might have been expected from other diffusion m easurements. It has previously been found that there is a tendency for self-diffusion coefficients obtained with fritted discs to be lower than those obtained with the conventional open-end capillary technique. Some possible sources of error are discussed.

Es werden die Ergebnisse von Tracerdiffusionsmessungen in flüssigem reinem Blei und Wismut sowie in einer Blei- Wismut- und einer Blei-Antimon-Legierung mitgeteilt. In diesen Schmelzen sind die Selbstdiffusionskoeffizienten von Blei und Wismut jeweils kaum verschieden. Das gleiche gilt für ihre Temperaturabhängigkeiten.