Band 23, Heft 6

A calculation is made of the cumulative effect of numerous small orbital perturbations caused by gravitational and collisional deflections of meteorites by other bodies in the asteroid belt. It is found that in a time equal to the age of the solar system the mean change in perihelion distance caused by gravitational perturbation is of the order of 10 -4 A. U. This phenomenon is consequently of negligible importance in removing meteorites from the asteroid belt. This conclusion is in disagreement with a result reported in the recent literature. The calculated mean change in perihelion distance caused by multiple collisional scattering is somewhat higher, about 10 -3 A. U. It is conceivable that a small fraction of very strong objects such as iron meteorites in highly inclined and eccentric orbits may be deflected into Mars-crossing orbits by this mechanism.

The polarographic investigation of Pb ++ , Cd ++ , Τl + , Zn ++ and Ni ++ ions in a KNO 3 -LiNO 3 -NaNO 3 molten eutectic mixture was carried out by conventional and oscillographic (single-sweep) polarography. Experiments were carried out in the temperature range 150 —200 °C, with a dropping mercury electrode as the cathode and a Ag/AgCl electrode as anode and reference. For ions with reversible behaviour (Cd + , Pb ++ , Tl + ) the polarographic diffusion coefficients calculated from conventional polarography data by means of the Ilkovič equation agree, within experimental errors, with those obtained from oscillographic data by the Randles-Sevčik equation at low potential change rates. At higher potential change rates deviations of the experimental peak currents from their theoretical values were observed. This is associated with a marked distortion of the wave and indicates a certain degree of kinetic control. The temperature dependence of the diffusion coefficients in the investigated range is the same for the ions with reversible behaviour and the corresponding activation energy is E= — 8.4 kcal/mole.

The open-circuit electrical potential of the solid galvanic cell : was measured between 1000 and 1400 °K. The measurements were carried out both in stationary and in non-stationary conditions after cathodic polarization of the Nb—NbO electrode, recording the e. m. f. decay curves. A comparison between the two sets of results was made and the conditions which assure the reliability of the tensiometric measurements under non-stationary technique were stated. The standard free energy of formation of niobium monoxide was then calculated from the experimental data. The discrepancies with the literature values of the standard enthalpy and entropy of formation were interpreted in terms of a significant homogeneity field of stability of the NbO phase.

In this paper further considerations has been given to the fluctuation model of diffusion, and equations have been derived which express the self-diffusivity of liquid metals as a function of temperature and pressure. For liquid metals which are characterized by pair potentials which are relatively deep compared with k T, D is predicted to vary in a linear fashion with T at constant volume. At constant pressure, the apparent activation energy is predicted to be equial to R T+R(β/β)T 2 where β is the isothermal compressibility and β' is its temperature derivative. Further, the variation in the logarithm of D with respect to pressure is predicted to be equal to [ (1/2.3)β] (∂β/∂P) T . A test of the equations for liquid mercury shows good correlation between theory and experiment. For liquid metals which are characterized by a shallow well in terms of the pair potential, no simple statements can be made concerning the nature of the temperature dependence, and simple approximations cannot be made. A test of the derived equations is made for liquid sodium which fits this case and for which good pair potential data exist, and good agreement is obtained at 373 °K. The temperature dependence of D as a function of T at constant volume is derived, but cannot be tested because of insufficient experimental data. The case of thermodiffusion is discussed, and it is shown that experimental values of the heat of transport are consistent with predictions of the theory.

A method has been developed to measure the rate of rapid heterogeneous ion exchange reactions between powdered solids and an aqueous solution within the temperature range from 100 to 180 °C. The principle of this method is the following: Both the preheated solid and the preheated aqueous solution are brought into contact by breaking a container. After an exchange period of ≧ 10 sec the process is interrupted within a time intervall of 0.2 sec by splashing cold alkohol ( — 115 °C) into the reaction vessel. By means of this “temperature-jump”-method the isotopic exchange in Ba-zeolite A has been investigated. The diffusion process was found to be not uniform at temperatures up to 100 °C just as already had been shown for Cs difussion in Zeolith A. Above 100 °C, however, it appears to become an ideal diffusion process exactly obeying the solution of the diffusion-equation for the relevant case over the entire range of the process.

The relaxation times of Zeeman and dipolar energies have been measured in a single crystal of CaF 2 containing Ce impurities at very low concentration. Measurements have been made at various temperatures between 4.2 °K and 77 °K. It is shown that the Zeeman energy relaxation passes from a rapid spin diffusion to a diffusion limited case when the temperature is increased whilst the dipolar energy relaxation seems to be diffusion limited over the whole temperature range.

By means of NMR- and EPR-spectroscopy we investigated the system benzene-sodium chloride. Using spin-echo techniques the proton relaxation time T 1 of the sorbed benzene has been measured as a function of proton resonance frequency in the interval between 10 kHz and 24 MHz for different temperatures (7 °C, 25 °C, 50 °C) . The benzene content was 0.16 g/ (g adsorbent) on ground and dried sodium chloride with a specific surface area of 0.1 m 2 /g. The two dispersion regions near frequencies of ω I /2 π = 24 MHz and ω I /2 ηπ = 460 kHz can be explained by magnetic proton-electron- and magnetic proton-proton-interaction respectively. In agreement with EPR-mea-surements the high-frequency step gives a transverse electron spin relaxation time τS2=1.1·10 -11 s of the paramagnetic impurities, while the relatively long correlation time τCA=3.5·10 -7 s from the low-frequency step can be connected with the stochastic reorientation of the benzene molecules adsorbed on active centers. A rough estimation of the activation energy for τCA yields a value of 1.4 ... 2.7 kcal/mole.

An der homologen Reihe der Diäthylester und einigen verwandten Molekülen wurde ε″ zwischen 30 und 0,7 cm Luftwellenlänge in verdünnter Benzollösung gemessen. Dem so ermittelten Teil der Absorptionskurve läßt sich ein Relaxationszeitspektrum nach Fröhlich zuordnen, dessen Mittelwert für Bernsteinsäurediäthylester größer als bei allen anderen Homologen ist. Das geht parallel zu einem besonders niedrigen molekularen Dipolmoment und wird als innere sterische Behinderung der Rotation von polaren Gruppen gedeutet. Bei Dicyclohexyl- und Dibenzyloxalat sind die Absorptionskurven unsymmetrisch, woraus auf die Beteiligung von sehr kurzen Relaxationszeiten an der Dipolorientierung geschlossen wird.

The infrared spectrum of H 2 S 2 has been reviewed in the range 4000 to 250 cm -1 and the spectrum of D 2 S 2 has been measured for the first time. No change in the basic assignment of the fundamental bands of H 2 S 2 has been made, although the stretching fundamentals and the combination bands can be more precisely assigned on the basis of the new information. With the six fundamental frequencies of H 2 S 2 and the two asymmetric fundamental frequencies of D 2 S 2 , calculations were made to determine as fully as possible the general valence force field. It was found that only the diagonal force constants could be determined on the basis of the available data: FSH = 4.08 - 4.09 md/Å, F a = 0.83 - 0.85 md A/rad 2 , FSS = 2.52 -2.62 md/Å, Ft = 0.0926 md Å/rad 2 .

Mit Hilfe der Fluoreszenz-, Fluoreszenzanregungs- und Phosphoreszenzspektren sowie der APF-, APPh-, FP- und PhP-Spektren wurde eine Zuordnung der Elektronenübergänge für die 10 isomeren Phenanthroline vorgenommen. Dabei zeigte sich wie in vorhergehenden Arbeiten, daß für die spektroskopischen Eigenschaften nicht die Symmetrie der Verbindungen, sondern nur die gegenseitige Stellung der beiden N-Atome in den äußeren Ringen entscheidend ist. Die Schwingungsübergänge für den Grund- und Anregungszustand werden diskutiert.

Aus dem genau zu bestimmenden Verhältnis der Quantenausbeuten der Phosphoreszenz und Fluoreszenz und den Phosphoreszenzabklingzeiten wird die Größenordnung der Geschwindigkeitskonstanten für die strahlungslosen Interkombinationsübergänge S 1 → T 1 und T 1 → S 0 abgeschätzt. Unter Verwendung der bekannten Quantenausbeuten des Phenanthrens werden ferner die Quantenausbeuten der Phosphoreszenz und Fluoreszenz für die Phenanthroline abgeschätzt.

Infrared spectra (300—4000 cm -1 ) have been measured on the octacyanide complexes K 4 Mo (CN) 8 ·2H 2 O and K 4 W (CN) 8 ·2 H 2 O in aqueous solution, in the solid dihydrates, and in the solid anhydrous compounds. Comparison with relevent Raman data, particularly in the 2100 cm -1 region, provides conclusive evidence for the effective molecular symmetry of the M (CN) 8 4- group in the different surroundings. In aqueous solution, the ions [Mo (CN) 8 ] 4- and [W (CN) 8 ] 4- assume the symmetry of an Archimedean antiprism, D 4d . In the dihydrate crystals, the groups Mo (CN) 8 4- and W (CN) 8 4- approach the full D 2d symmetry of a dodecahedron with triangular faces, possibly slightly distorted by packing effects. In the anhydrous compounds, the symmetry of these groups is considerably lower, very likely C 8 . Reasonable assignments for all normal frequencies in the 2100 cm -1 region are proposed, both in D 4d and D 2d symmetry.

Die Änderung der Wärmeleitfähigkeit λ von Ni und Ni—Cu-Legierungen im Magnetfeld verläuft unterhalb der magnetischen Sättigung völlig parallel zur Änderung der elektrischen Leitfähigkeit σ. Oberhalb der Sättigung nimmt λ sowohl bei H parallel als auch bei H senkrecht zum Wärmestrom mit zunehmendem H ab, wogegen σ zunimmt. Dieser Effekt wird mit dem experimentell beobachteten Anstieg von λ oberhalb des Curie-Punkts und mit der magnetischen Beeinflußbarkeit der spez. Wärme in Zusammenhang gebracht.

In a stationary high density d. c. arc, the electric power input is balanced essentially by heat conduction losses in radial direction. These losses increase greatly with temperature and thus they limit the axial temperatures attainable with reasonable power input. An experiment is described in which considerably higher plasma temperatures have been obtained by reducing the coefficient of heat conduction with a superimposed axial magnetic field. At arc currents of about 2 kA and a magnetic field of 10 kG temperatures in the middle of the arc of the order of 10 eV were reached. The measured temperature, pressure and power input of the hydrogen plasma are compared with calculated values. In particular, the coefficient of heat conduction perpendicular to a magnetic field has been determined by measuring the radial temperature profile and the electric field strength. The results agree with theoretical predictions.

The axial and radial components of the electric field in a hydrogen arc with superimposed axial magnetic field have been measured with potential probes. The axial field was found to be only 3.1 V/cm, whereas in the radial direction fields up to 400 V/cm indicate a rotation of the arc. Radial fields are caused by υ x 23 e. m. forces due to this rotation. The probe measurements indicate velocities of the order of 10 6 cm/sec which are confirmed by Doppler shift measurements. A simple model is considered in which Lorentz forces cause a rotation of the arc; calculations are in agreement with the measurements. Axial velocities (2 · 10 4 cm/sec) have also been determined, by measuring the velocity of a perturbation due to the probe. This perturbation travels downstream in the arc and is observed as a small drop in the arc voltage passing the anode region.

The absorption and ionization cross sections of molecular hydrogen for the wavelength region from 850 to 792 A are given. This region contains the dissociation and ionization limit as well. The rotational structure of the bands could partially be resolved in this experiment. As the dissociation of the molecule results in an excited hydrogen atom, this process can be followed by measuring the atomic fluorescence. Part of the excited atoms is found to be in the metastable 2 2 S-state. From fluorescence as well as absorption and ionization measurements it can be shown, that even above the ionization limit the absorption due to the D-state of the molecule leads to dissociation. The experimental results seem to point out, that the spectroscopic value of the ionization limit has to be shifted to lower energies.

Es wurde das Verhalten einer Trennrohrstaffel theoretisch und experimentell untersucht, bei der an einer Stelle die Breitenfunktion gegen das Entnahmeende hin zunimmt. Dieser Sachverhalt hängt eng mit dem Effekt zusammen, daß bei großen Entnahmen unter Umständen der Konzentrationsgradient in der Längsrichtung in Teilen der Anlage seine Richtung umkehren kann. Es zeigt sich, daß man daraus eine exakte Methode zur Bestimmung des Anfangstransportes herleiten kann.

Betrachtet werden zwei druckfeste Kammern, die durch eine Kapillare miteinander verbunden sind und mit einem Gasgemisch aus zwei Komponenten verschiedener Konzentration gefüllt sind. Der Konzentrationsunterschied ruft Diffusion hervor, die durch die damit verbundene Schwerpunktsverschiebung und durch den Einfluß der Kapillare mit der Zeit einen Druckunterschied aufbaut. Die dadurch verursachte Druckdiffusion wirkt der Diffusion entgegen. Es wird die Möglichkeit aufgezeigt, den Diffusionskoeffizienten und den Druckdiffusionskoeffizienten aus einem Experiment zu bestimmen. Das Problem wird unter Vorgabe von drei verschiedenen Konzentrationsverteilungen zu Beginn des Versuchs berechnet. Es wird ferner gezeigt, daß unter gewissen Annahmen diese verschiedenen Anfangsbedingungen keinen Einfluß auf das Ergebnis haben. Diffusions-, Druckdiffusionskoeffizient, partielles Molvolumen und Molvolumen der Mischung werden bei der Berechnung als unabhängig von Zusammensetzung und Druck angenommen.

On the basis of the Waldmann equation for neutral particles with spin, the influence of a homogeneous magnetic field on spin-diffusion in a gas has been studied. The spin-diffusion constant for the components of the magnetic moment perpendicular to the external field is decreased. Furthermore a transverse spin-flux is found which leads to a shift of the resonance frequency if the magnetization is spatially inhomogeneous. Both effects vanish at high densities.

The theory of solution for quantum field functional equations is developped for a suitable testproblem of quantum mechanics. In Sect. 1 the functional formulation of the anharmonic oscillator in its spinorial representation is given, and in Sect. 2 translational equivalent functional equations are discussed. The expansion of the physical state functionals into series of basefunctionals and the symmetrical representation of the functional equations for such an expansion is discussed in Sect. 3. In the following Sect. 4 the special symmetric orthogonal Hermitean functionals are used and the explicit representation is derived. In Sect. 5 the functionals are approximated by expansions with only a finite number of terms and the resulting equations are prepared for integration and in Sect. 6 a necessary condition of stationarity is considered. In Sect. 7 the simplest equation for N=1 is discussed in detail and the lowest eigenvalue is obtained. In the appendices technical details are derived.

HFS-Nullfeldresonanz ist Elektronenspinresonanz im Feld eines Kernspins ohne äußeres Magnetfeld. Sie bietet eine Möglichkeit, den Hyperfeinkopplungstensor, d. h. die Konstanten der magnetischen Kopplung zwischen Elektronenspin und Kernspin, direkt aus dem Nullfeldspektrum der polykristallinen bzw. amorphen Substanz zu bestimmen. Die Übergangsfrequenzen liegen z. B. bei Kopplungen zu Protonen im Bereich bis ca. 200 MHz. Es wird hier der Aufbau eines Nullfeldspektrometers für Frequenzen zwischen 12 MHz und 80 MHz beschrieben. Die Anwendungsmöglichkeiten der HFS-Nullfeldresonanz werden an Hand von Messungen an bestrahlten Substanzen diskutiert, wobei in den vorliegenden Fällen die Aufklärung der Strahlenschäden im Vordergrund steht.

The electrical conductivity of molten (Na—Rb)NO 3 and (Tl—Rb)NO 3 was determined. While the equivalent conductivity of the first system shows the usual negative deviation from additivity, that of the second one varies nearly linearly with composition. After discussing the conductivity isotherms in terms of some proposed models, an excess conductivity isotherm is presented, derived on the basis of simple assumptions about the trend of both cationic mobilities.

A comparison between the available self-diffusion data on pure molten salts and the predictions by different liquid diffusion theories is made. It is found that the Arrhenius equation D=D 0 exp (— Q/R T) describes the experimental data equally well (or better) than any of the other theoretically predicted equations. The hole model prediction (Q=3.74 R T m ) is found to be inaccurate. The free volume model and the local density fluctuation models describe the data less well than the other models considered. The cubic cell model leads to a correct correlation between self-diffusion and kinematic viscosity for several salts (but not all).

Electron energy loss measurements on polycrystalline KBrfilms are reported. Excitonic structure is found to be associated not only with the top valence band but also with deeper bands (K + 3p-level). The spin-orbit splitting of this state is resolved.