Band 25, Heft 3

The method of "specific decoupling", as described in two earlier papers, is applied to special forms of wave functions of the 3-body-problem. The internal frame of reference, connected with a collective rotational motion of the system, is determined by solution of the basic differential equation. An exact expression for the effective moment of inertia is given and evaluated. The results confirm the validity of former variational calculations

A statistical theory of the intercomponent transport processes is given for nonisothermal plasmas consisting of electron and ion components, when the particles interact through Coulomb collisions screened electrostatically beyond the Debye-radius. The associated collision integrals are evaluated analytically for arbitrary drift velocities of the components, and under consideration of the velocity dependence of the Coulomb logarithm. The resultant analytical relations form consistent mathematical foundations for a transport theory of systems with collisional Coulomb interactions. It is shown that different properties of the transport processes and the effective Coulomb logarithms result for subsonic and supersonic drift velocities of the components

We discuss the general procedure of diagonalizing a field-theoretical Hamiltonian in the special case of a multi-channel scattering problem in which the asymptotic fields and the interpolating field are connected by a non-unitary transformation

The rotational angular momentum dependence of the nonspherical scattering amplitude is investigated for inelastic collisions of linear molecules. As far as the approximation of small nonsphericity can be applied, this dependence is obtained from the angular momentum dependence of the nonspherical interaction potential. The connection between the nonspherical scattering amplitude and observables that can be measured by molecular scattering experiments involving a polarized beam is discussed. Some qualitative remarks are made on collision brackets occurring in the theoretical expressions for the bulk viscosity and for the Senftleben-Beenakker effect for H 2 and HD

The spectrum of the depolarized Rayleigh light scattered by a gas of linear molecules is calculated by a kinetic theory approach based on the Waldman-Snider equation. Collisional and diffusional broadening are studied. The line width is related to relaxation coefficients which are collision brackets obtained from the linearized Waldmann-Snider collision term involving the binary molecular scattering amplitude and its adjoint. It is shown under which conditions the relaxation coefficients characterizing the line width can be compared with data obtained from Sentfleben- Beenakker effect and nuclear magnetic relaxation measurements

Twelve six-atomic models are treated as a part of the work on tentatively standardized symmetry coordinates of molecular vibrations

By use of Green's functions for the diffusional motion a very concise formulation and computation of correlation functions is possible. For an axially symmetric overall diffusion with internal rotation about one and two axes correlation functions of a second rank spherical tensor are calculated. The results comprise all the solutions of the pertinent problem as given so far and allow the extension of the theory to a wider field of application

Es wird der Zusammenhang zwischen den konzentrationsabhängigen Diffusions- und Sedimentationskoeffizienten (D und s) für Salzschmelzen untersucht. Zuerst werden Salzschmelzen mit zwei Komponenten betrachtet, die aus drei ionischen Bestandteilen bestehen, also Salzschmelzen mit gemeinsamem Anion oder Kation. In solchen Systemen lassen sich D und s unabhängig vom Bezugssystem definieren. Die entsprechenden Gleichungen im Fickschen und in den drei Hittorfschen Bezugssystemen und die Transformationsgleichungen zwischen diesen Bezugssystemen werden beredinet und der vom Bezugssystem unabhängige Zusammenhang zwischen D und s ermittelt. Bei Salzschmelzen mit mehr als zwei unabhängig wandernden ionischen Bestandteilen, audi wenn die Schmelze nur aus zwei neutralen Komponenten besteht, hängen D und s sowie ihre Relation zueinander vom Bezugssystem ab

Drift-current-pulses in semiconductors with vanishing dark conductivity measured according to the method of Kepler and LeBlanc deviate from the expected rectangular pulse shape even under ideal experimental conditions. In this work it will be shown that among other processes the diffusion of current carriers is responsible for the deviation. Under appropriate experimental conditions one is able to measure diffusion-constants in anthracene by a method to be described. Within experimental error the diffusion-constant obtained agrees with the value calculated from the Einsteinrelation using the independently measured drift-mobility. The differences in method from the known techniques used with dark conducting semiconductors are discussed. The measurements succeed only with very good crystals for which quality criteria are given

Brillouin-Streuexperimente in SrTiO 3 im Bereich der Phasenumwandlung von der kubischen zur tetragonalen Struktur werden mit Hilfe eines Modells für den Phasenübergang gedeutet, das Ergebnisse liefert, die der Theorie von Landau und Khalatnikow entsprechen. Die Phasenänderung wird als Ubergang 2. Ordnung betrachtet, bei dem die beobachteten akustischen Effekte unterhalb der Umwandlungstemperatur auftreten. Als Temperatur des Phasenüberganges wird der Wert 107 + 0,5 °K ermittelt. Die Größe der Stufe in den Brillouin-Verschiebungen konnte aus Literaturdaten, wie Änderungen der Gitterparameter, Drehwinkel der Sauerstoffoktaeder, soft-mode-Frequenzen, vorhergesagt werden. Die Übereinstimmung mit den experimentellen Ergebnissen ist zufriedenstellend. Die Messungen legen eine verhältnismäßig geordnete Domänenstruktur der untersuchten Kristallproben in der Tieftemperaturphase nahe mit einer Domänenorientierung entlang den Achsenrichtungen der kubischen Phase und überwiegend antiparallel ausgerichteten tetragonalen Domänenachsen. Die beim Anwenden einer äußeren Spannung im Brillouin-Spektrum beobachteten Änderungen werden als Umorientierung der Domänenachsen gedeutet

The flux density and the velocity of hydrogen cluster beams are measured with nozzle temperatures between 34° and 39 °K and with inlet pressures between 15 and 35 atm. At a distance of about 20 cm from the nozzle exit number densities as high as 1 x 10 18 H 2 -molecules/cm 3 are found within a background density of about 5 x 10 10 molecules/cm 3 . The degree of condensation is calculated from the measured kinetic energy of the beam particles and the known enthalpy of the gas before the expansion assuming that the final thermal energy of the expanded material can be neglected. Within the cited intervals of temperature and pressure degrees of condensation between 8 and 29% were found

Molecules in certain excited states can be forced to predissociate in an external electric field. This effect will be shown to occur with H 2 and D 2 . The molecular dissociation is made possible by an altered coupling mechanism as compared to the mechanism considered for the Kronig's selection rules. The interaction is a linear function of the field strength. It is further demonstrated that also molecular fields (van der Waal's fields) may cause the effect which is shown by the collision induced predissociation of the excited molecular states under consideration

An automatical recording spectroscopic arrangement was developed to measure the side on distributions of the emitted light of spark channels at different times of the channel development. The radiation at two wavelengths was detected by means of two photomultipliers. The photomultiplier currents are applied to a two channel sampling unit which measures the amplitude of this currents at a fixed selected point of time. The output voltages of the two sampling channels are applied to the a:-inputs of two xy-plotters. By means of an image converter and a television scanning system it was possible to determine that part of the spark channel from which the photomultiplier had received the light. The scanning system produces an output voltage which is proportional to the radial distance of this observed part from the channel axis. This voltage is given to the y-inputs of the two xy-plotters. The spark channels are initiated "shot by shot" using a pulse generator, and the xy-plotters write down the side on distribution "dot by dot" for a fixed point of time. A programmable control and regulating system checks the whole measuring process

In a streamer initiated pre-discharge channel in H 2 the axial and radial electron density distributions were measured at different times of the channel development. It was found that at any point in the channel where the electron density reaches ≅ 2 - 10 17 cm -3 an immediate thermalisation of the plasma at this point takes place in a time of ≅ 10 nsec. Due to the inhomogeneous radial and axial electron density distribution in a streamer initiated discharge channel the thermalisation begins at first in a constricted region of the channel. The further development of the electron density and temperature distributions in the thermalized channel was studied by means of spectroscopic plasma diagnostic methods in channels initiated by different overvoltages. These experiments have shown that the inhomogeneous axial electron density distribution is equalized after a time of ≅ 100 nsec. The maximum electron density of ≅ 1 - 2 - 10 18 cm -3 is reached in the channel axis immediately after the thermalisation of the channel whereas the temperature increases during the time of the highest energy input to the maximum of ≅ 5 - 6 • 10 4 °K

Measurements were carried out in order to investigate the temporal behaviour of temperatures in the channel axis of sparks in hydrogen in which different amounts of energy were released. It was found that with increasing energy input the temperature rises to approximately 60 000 °K . A further enhancement of temperature above this value could not be observed in spite of increasing energy dissipation. This effect can be explained by the fact that an increasing amount of the released energy is converted into expansion energy. The temporal development of the channel radii was measured and was compared with calculated values using Drabkina's and Braginskii's theories. Good agreement between measured and calculated radii was found

In Fortführung unserer Arbeiten über die Elektronenspektren von N-Aryl-carbazolen 1, 2 haben wir das N- (β-Naphthyl) -carbazol (Strukturformel siehe Tab. 1) untersucht. Die bislang in der Literatur nicht beschriebene Verbindung wurde aus Carbazol und 2-Jod-naphthalin mit einem Verfahren, das sich bei der Herstellung anderer N-Aryl-carbazole bewährt hat 3 , dargestellt

The nuclear quadrupole resonance (NQR) transitions of 35 Cl and 37 Cl have been detected in polycrystalline LiClO 3 . Precision measurements have been performed at 26 °C; some preliminary investigations at different temperatures have been made

The Cini-Fubini approximants are equal to the diagonal Pade approximants to the S-matrix. In this paper a simple proof of this statement is given

The mean life time, T, of the excited state of the n → π* transition of the nitrate ion in different solvents has been estimated from a spectrophotometric study. These T values are by a factor of 10 -3 - 10 -4 smaller than computed values for vibration perturbation. The values decrease with increase in the hydrogen bonding power of the solvent. Hydrogen bonding perturbation has been suggested to be the cause of the observed life time of the excited state

Approximate closed expressions for the mean values of nuclear shielding constants and the diamagnetic susceptibility of 1 Σ molecules are given which apply if a density matrix constructed over a set of pure Gaussian functions, is known