Band 26, Heft 10

By means of the levelcrossing method the hyperfine structure constants and the lifetime as well as the angular momentum of the term 29607.98 cm -1 of LuI were determined. This term can be assigned to the 6s 2 7p 2 P 3/2 -state. The signs of the interaction constants were obtained by the investigation of the line 3376.5 Å from this state into the 5d6s 2 2 D 3/2 ground state in a Fabry-Perot interferometer. Together with the measured branching ratio from the lifetime the oscillator strengths were found. The results are: J = 3/2; B/| A | = 0.4947 (4); τ = 0.512 (16) · 10 -8 (1.24/gJ) s; A = 678.94 (2) gJ/1.24 MHz; f(3376.5 Å) = 0.382 (15); B = 335.9 (3) gJ/1.24 MHz; f(3620.3 Å) = 0.15 (4) · 10 -2 .

The magnetic field at the site of the nuclei 152 Sm and 154 Sm in a ferrimagnetic Sm 6 Mn 23 probe has been measured by means of the perturbed angular correlation method after Coulomb excitation. The temperature dependence of the magnetic field has been investigated and compared with the results of macroscopic experiments. It can be concluded from the present work that the magnetic field H eff (T) at the site of the Sm nuclei is proportional to the macroscopic magnetisation J (T). We obtained a ferrimagnetic Curie Temperature of T C = 438(5) K in good aggreement with macroscopic values and H eff (T=0 K) = 1300(50) kOe.

The 6 S 5/2 ground state of Mn 55 was polarized by spin exchange collisions with an optically pumped Cs-vapour. The rf induced transitions between Zeeman subleves of Mn were detected as a change in the Cs pumping light transmission. To estimate the effectiveness of direct optical pumping or of detection with resonance light the absorption probabilities for circlarly polarized light are given as functions of 〈S z 〉.

Two methods are described to derive cross sections for spin exchange and spin depolarization of an indirectly pumped alkali vapor with zero nuclear spin. Either pulsed or sinusoidally modulated radiofrequency can be used to destroy the polarization of the indirectly pumped (secondary) system, while the intensity of the transmitted pumping light is observed. Cross sections follow from the indirectly produced depolarization of the primary system i. e. from the change in pumping light transmission or from the phase angle between the rf modulation and the intensity oscillations of the transmitted light. The quality of the two methods is tested by deriving cross sections for spin exchange between Cs and Rb and for depolarization of Rb in Argon buffer gas.

By treating the hindered methyl group rotation in solids quantum-mechanically the proton spin lattice relaxation at low temperatures is calculated in first and second order. For low hindering barriers (smaller than 1 kcal/mole) significant differences from the usual relaxation theory are obtained. The inverse correlation time 1/τ 0 is essentially given by the rate of non magnetic transitions between the zeroth and first torsional state; and as a consequence the apparent activation energy at low temperatures is given by the difference between these levels. For a given To the relaxation is by a factor ω 0 /Λ 0 (Λ 0 is the tunneling frequency) less effective than in the classical case. Good agreement between earlier measurements and this theory is obtained by considering at low efficiency factors also the magnetic interaction between the methylprotons and the surrounding protons. In this way the experimentally observed two relaxation maxima and the ω 0 -dependence can be explained too.

This paper describes EPR measurements within the system CdF 2 : Eu 2+ between 77 K and 300 K at 9 GHz and 35 GHz for B || [001]. The measurements enable a test of the formerly determined EPR parameters by the strict numerical solution of the eigenvalue problem including the hyper-fine terms. In particular “forbidden” transitions (ΔM = 2) also occur in a strict cubic crystalline field. An interpretation of the superhyperfine structure at 9 GHz and 35 GHz is compatible with the constants T || = 6.26 MHz and T | = - 6.04 MHz of the interaction with the F ions of the 1 st shell.

In a beam experiment the processes of elastic scattering, pure rotational excitation and deexcitation, pure vibrational excitation, and simultaneous rotational-vibrational excitation have been investigated for e-H 2 scattering in the energy range from 0.3 eV to about 15 eV. Differential and integral cross sections have been determined in arbitrary units and calibrated on an absolute scale by normalization to absolute total cross sections. The results are discussed in terms of super-position of direct scattering, shape resonance and Feshbach resonance scattering and are compared with recent theoretical investigations. The cross sections for rotational and vibrational excitation, which are generally small for direct scattering, are greatly enhanced by a broad shape resonance near 3 eV and by Feshbach resonances around 12 eV. Characteristic differences in the excitation mechanisms are discussed.

Elastic scattering, vibrational excitation to v=1, 2, 3, 4 of the electronic ground state, and electronic excitation to the states a 1 Δ g and b 1 Σ g + of O 2 have been measured in a crossed beam apparatus for collision energies from nearly 0 eV to 4 eV. Differential and integral cross sections have been determined and calibrated on an absolute scale. From 15 vibrational levels of O 2 - , which could be observed as resonances in the cross sections, the spectroscopic constants for the vibrational structure of O 2 - have been derived: ω e = 135 meV and ω e χ e = 1 meV. The cross sections for vibrational excitation have the order of 10 -18 cm 2 . eV for the larger resonance peaks. Detailed cross sections have been listed in Table 1. The half width of the resonance can be estimated to Γ ≈ 0.5 meV, which corresponds to a lifetime tof 10 -12 sec for the O 2 - states. The angular dependence of pure resonance scattering is rather flat and not in accordance with the simplest theoretical model. An analysis of the angular dependence and of the rotational structure of the resonance in a somewhat extended model have been performed. - No electronically excited O 2 - states could be detected in the energy range up to 3 eV.

A diagrammatic technic is presented which is appropriate to study the nonlinear response of the collision dominated solid state plasma to randomly phased ac fields. By summation of diagrams, a nonlinear integral equation is established for the propagator S′ which is directly related to the nonlinear response function. Using the equation for S′, an equivalence is derived between a model solution in the theory of nonlinear coherent ultrasound amplification and the interaction theory of a great number of randomly phased vibrational modes, confined to a small frequency band.

The contribution of the vibration-rotation interaction term to the potential results in the fact that each rotational level has a slightly different potential curve. These deformed curves are used to integrate the Schrödinger equation.

A new calibration method for slotted disk velocity selectors is presented and is compared with other calibration procedures. It is based on the measurement of the velocity distribution of a supersonic molecular beam produced by a room temperature source. The error due to the assumed theoretical distribution and to experimental procedure is discussed. It is shown that the velocity scale is known to within 0.8%.

Due to the coupling between the rotational angular momentum and the electronic spin, the depolarized Rayleigh light scattered from gaseous oxygen shows Stokes and anti-Stokes satellites shifted by about 60 GHz. The broadening of these fine-structure Raman lines is investigated theoretically for high and medium pressures where the linewidth is determined by two contributions, one proportional and the other inversely proportional to the pressure, p. The linewidth in the pressure broadening region is given by a relaxation frequency which is obtained from the Waldmann-Snider collision term. The p -1 contribution to the linewidth is determined by the ratio of the second moment of the fine-structure freqencies (with respect to the center of the shifted line) and another relaxation frequency. Both relaxation frequencies are sensitive to the nonspherical part of the inter-molecular potential.

The molecular Zeeman effect has been observed in the rotational spectrum of 2-fluoropyridine at magnetic fields close to 25000 G. The measured molecular g-values are g aa = -0.0880 ± 0.0007, g bb = - 0.0405 ±0.0006, g cc = + 0.0233 ±0.0006, and the two linearily independant components of the magnetic susceptibility anisotropy are 2 · χ aa - χ bb - χ cc = 50.5 ± 1.6 and 2 · χ bb - χ cc - χ aa - 53.8 ± 1.1 in units of 10 -6 erg/G 2 mol). The a-axis is close to the C-F-bond and the c-axis is perpendicular to the plane of the ring. A comparison of the gas-phase out-of-plane minus the average in-plane values for the susceptibilities of 2-fluoropyridine, pyridine, and fluorobenzene with the corresponding value for benzene in crystalline phase leads to the conclusion that the susceptibilities may change in the order of 10% when going from solid or liquid phase to the gasphase. A short description of the microwave-Zeeman spectrograph built at Kiel University is given. In the theoretical section expressions for the g-values and susceptibilities are derived which are more complete then those used up to now.

A detailed analysis of the molecular structural data and infrared absorption and Raman spectra of the hexafluoride of sulfur, selenium, tellurium, molybdenum, technetium, ruthium, rhodium, tungsten, thenium, osmium, iridium, platinum, uranium, neptunium, and plutonium has been made. These molecules, having the greatest number of symmetry elements of all existing molecules, possess an octahedral symmetry with the symmetry point group Oh. They give rise to six fundamental frequencies of which three are allowed in the Raman spectrum, two are allowed in the infrared absorption spectrum, and one is inactive. The inactive mode in normally determined from the overtones and combinations. On the basis of a rigid rotator and harmonic oscillator model, enthalpy, free energy, entropy, and heat capacity for temperatures from 200 °K to 2000 °K have been computed for these molecules. The results are briefly discussed and compared with available experimental data.

An approximate method is described for calculating electrostatic fields of rotational symmetry with arbitrary boundary conditions. The method is based on the computation of the surface charge density on the field forming electrodes. Successfully tested by well-known analytical solutions, the method is applied to the determination of electron trajectories in an electron gun with a point cathode. The ray tracing is done by the Runge-Kutta-Nyström procedure.

The electron-phonon-interaction is investigated within the RPA-scheme taking into account the local field of the crystal. In order to describe the screening by the conduction electrons an integral equation is solved in the limit of long phonon-wavelength. In contrast to the usual procedure, which is based on the deformation potential, the form factor of the ion potential and the electron wavefunction are needed in the present calculation. In the case of sodium the latter are calculated by the OPW method. Neglecting virtual interband transitions the T 5 -coefficient is found to be enlarged by 30% due to the local field. The result cannot explain the existing discrepancy of a factor 3 between experimental and theoretical resistivity.

Für CeRu 2 und seine Mischkristalle mit den Rutheniden anderer seltener Erdmetalle wird nach drei Methoden ein Wert für die effektive Austauschwechselwirkung J eff ermittelt: Aus der g-Ver-schiebung, aus der Konzentration c 0 , die den supraleitenden Konzentrationsbereich begrenzt, und aus Curietemperaturen. Die beiden ersten Methoden ergeben ein J eff von einigen meV, nach der dritten Methode ist J eff merklich größer. Es wird angenommen, daß die Ursache für die geringe T c -Absenkung durch magnetische Ionen der seltenen Erdmetalle ein kleines J eff ist und nicht die Wechselwirkung der Ionen mit Kristallfeldern.

CdTe-Schichten wurden auf verschiedene Weise hergestellt und elektrische und photoelektrische Eigenschaften untersucht. Durch Verdampfen der Verbindung hergestellte Schichten zeigten den Hochvolt-Photovolt-Effekt, die höchsten Spannungen traten für In-dotierte Schichten auf. Durch gleichzeitiges Verdampfen der Komponenten Cd und Te (Dreitemperaturverfahren) erhaltene Schichten zeigten diesen Effekt nicht. Die günstigsten Herstellungsparameter wurden ermittelt. Durch gleichzeitiges Verdampfen von In oder Nachbehandlung der Schichten im Cd-Dampf wurden die elektrischen Widerstände durch Donatordotierung herabgesetzt. Gleichzeitige Dotierung mit Cd und In lieferte die niedrigsten Widerstände. Aus auf Molybdän-Substraten durch Komponentenver-dampfung erhaltenen CdTe-Schichten wurden durch Bildung von n-CdTe -p-Cu 2 Te-Heteroüber-gängen Solarzellen hergestellt. Dabei wurde der Einfluß verschiedener Dotierung mit Cd, In oder Cd + In untersucht.

Amorphes Se ist gitterähnlich. Weitere gitterähnliche amorphe Stoffe sind: Si, Ge, As, Sb u. a. m. sowie die Gläser SiO 2 , B 2 O 3 u. a. m. Diese amorphen Stoffe haben mit dem zugehörigen Gitter den Grundbaustein, das Bauelement, gemeinsam. Bei Se hat man die drei amorphen Formen Se(I), Se(II) und Se(III) mit verschiedenem kürzestem Kettenabstand zu unterscheiden. In Se(I) kommen Schraubenketten wie im Gitter vor, in Se(II) und Se(III) dagegen ebene Zickzackketten mit dem Elementardreieck des Gitters als Baustein. In aufgedampftem amorphem Se findet man bei tiefer Temperatur Se(II) und bei Zimmertemperatur Se(III). Geschmolzenes Se von 270 °C baut sich vornehmlich aus Se(III) auf, daneben trifft man kleinste Gitterbereiche, also Se(I), an. Diese Struktur, und zwar mit denselben Komponenten, beobachtet man häufig bei glasig erstarrtem Se. In geschmolzenem Se von 425 °C liegt eine stark gestörte Kettenstruktur vor, so daß sich nur noch die Abmessungen des Elementardreieckes in der Atomverteilungskurve abzeichnen.

It is shown that the work of Cercignani and Tironi on Maxwell's boundary conditions method can be improved in a simple and logical way. The technique for improvement is illustrated by a study of the linearized plane Couette flow problem and it is found that the proposed modification yields results that are identical with some highly accurate variational results.

Liquid-liquid equilibria in binary systems of nitromethane with 1-(C 8 -C 9 )-, trans-2-(C 5 -C 9 )-, trans-3-(C 6 -C 9 )-, trans-4-(C 8 -C 9 )-, 3-methyl-1-(C 5 )-, 2-methyl-2-(C 5 -C 7 )- and cis-2-(C 6 )-alkenes were investigated. Some regularities obeyed by the critical temperatures and compositions, as well as the possibility of foreseeing (on empirical basis) the two liquids region boundaries are discussed.

The equivalent conductivity of molten salts containing more than two ion constituents will be discussed using the equivalent fractions (Äquivalentanteile). The ionic conductivities of the ion constituents follow from this equivalent conductivity and the transport numbers. The electrical transport phenomena are referred to the idealized ionic melt which is defined by the limiting values of the ionic conductivities of the ion constituents in the pure components. The equations are calculated for the system KNO 3 +AgNO 3 . Es wird die Äquavilentleitfähigkeit bei Salzschmelzen mit mehr als zwei ionischen Bestandteilen mit Hilfe von Äquivalentanteilen diskutiert. Aus dieser Äquivalentleitfähigkeit und den Überführungszahlen ergeben sich mit den Äquivalentanteilen die Ionenleitfähigkeiten der ionischen Bestandteile. Die elektrischen Transportphänomene werden auf eine idealisierte Salzschmelze normiert, die mit den Grenzwerten der Ionenleitfähigkeiten der ionischen Bestandteile in den reinen Komponenten definiert wird. Die Gleichungen werden berechnet für das System KNO 3 +AgNO 3 .

Dynamics of quantum field theory can be formulated by functional equations. To develop a complete functional quantum theory one has to describe the physical information by functional operations only. The most important physical information of elementary particle physics is the matrix. In this paper the functional S-matrix is constructed for nonrelativistic spin 1/2 fermions, as in this system a rigorous construction of operator representations is possible. The method of S-matrix derivation used in I and II is improved and the exact perturbation solution for the scattering functionals is given.

Dynamics of quantum field theory can be formulated by functional equations. To develop a complete functional quantum theory the physical information has to be given by functional operations only. The most important physical information of elementary particle physics is the S-matrix. In this paper the functional ^-matrix is constructed for the scattering of relativistic dressed particles, i.e. for particles with structural properties. The basic functional equation is assumed to be derived from a nonlinear spinor field equation with noncanonical relativistic Heisenberg quantization. The initial free dressed many particle states are defined, and the scattering functionals are constructed. By the use of irreducible representations the equivalence of the functional S-matrix with the conventional Hilbert space definition is shown with respect to an appropriate definition of the functional scalar product. Technical details are discussed in the appendices.

We examine the possibility of reformulating quantum theory (QT) as a deterministic ensemble theory which (a) interprets observables as objective properties of physical systems and (b) coincides with QT in all quantitative statements. As will be demonstrated, such an Ensemble-Quantum-Theory (EQT) can only be constructed if (1) one accepts a modified observable-concept, and (2) as long as the theory of measurement is left out of account. A correct treatment of the measuring process is impossible within such an EQT. Consequently, there exist no Hidden-Variable Theories with the properties (a) and (b).

A method for computing force-free magnetic fields of known anomality a ≠ const is described. The procedure is introduced by treating plane fields; thereby it is proved that force-free fields of constant strength are alyaws plane. In general case the surfaces a= const are chosen as coordinate surface of an orthogonal curvilinear coordinate system. In this system the magnetic field is described by a linear partial differential equation which can be solved numerically. Making use of simplifying assumptions about symmetries in the coordinate systems, analytic solutions are found which are extended on constant a. The formulae derived can be used to decide if to a given geometry a force-free field does exist. Existing fields can be computed immediately. The results are illustrated by examples.

Inversion formulas are given for determining the density of states by tunneling conductance measurements.

Some former measurements are reviewed concerning a secondary maximum occurring at the high-temperature side of the usual Hopkinson peak if a dc-magnetic field is superimposed parallel to the ac-field. Since, with regard to single domain particles embedded in a paramagnetic matrix, the measuring signal is proportional to the high-frequency losses, a secondary maximum indicates some kind of resonance phenomenon which obviously fulfills the geometrical conditions of parallel pumping experiments. It is shown that all other aspects of the experimental results also can be explained sufficiently if being interpreted in terms of parallel pumping theory.

All elastic and thermoelastic constants and the coefficients of thermal expansion of monoclinic SnF 2 are measured. These properties deviate strongly from the behaviour of other difluorides such as CaF 2 and MgF 2 . The high anisotropy, the large bulk compressibility and the departures from the Cauchy relations suggest the existence of strong covalent binding components between tin and fluorine atoms. The thermal properties are in accordance with Grünseisen's rule.

The numerical properties of 2 equivalent formulas for centrifugal distortion analysis are discussed The numerical results for 1-Chlor-3-Fluor-Propin and Dimethylsulfoxide show that the alternative formula to Watson's commonly used formula is numerically more stable by several orders of magnitude.

A method of concentration profile measurement of luminescent ions by ion sputtering has been applied to detect the boundary between alkali ions of glass wafers, which were contacted anodically by acid solution, and succeeding hydrogen ions after the application of an electric field. The transport number of lithium ions was found to be unity. Mobilities at 25 and 50 °C agree with data obtained from conductivity measurements. From the conductivity change during transport the mobility of succeeding hydrogen ions is also evaluated.