Volume 29, Issue 1

Using a selfcoupled spinorfield (Fermicoupling) as a model to describe relativistic nucleon-nucleon scattering it is shown that the functional S -matrix construction for relativistic clusters in nonlinear spinortheory proposed by Stumpf reproduces in lowest order perturbation theory the result obtained by usual quantum field theoretical methods.

The conversion electron spectrum of the reaction 155 Gd (n, e) 156 Gd has been measured up to 8.5 MeV. The results below 4.5 MeV are presented and multipolarities are determined with these results. E0 admixtures of the Δ I = 0 transitions from the 0 + β-vibrational band to the ground state band were determined with 15% accuracy. 156 Gd level schemes are discussed and extended by new spin and parity assignments.

The complete ligand field -Coulomb repulsion -spin orbit interaction matrices have been derived for the d4 and d6 electron configurations within octahedral (O h ) and tetrahedral (T d ) symmetry. The calculations were perform ed in both the weak-field and strong-field coupling schemes and complete agreement of the results was achieved. The energy matrices are parametrically dependent on ligand field (Dq), Coulomb repulsion (B, C) and spin-orbit interaction (ζ). Correct energy diagrams are presentend which display the splittings by spin-orbit perturbation as well as the effect of configuration mixing. Applications to the interpretation of optical spectral data, to the detailed behavior at the crossover of ground terms, and to complete studies in magnetism are pointed out.

The profiles of the first three Balmer lines of hydrogen are measured in a turbulent heating experiment. From the position of Stark satellites the field strength of low frequency oscillations (ω ~ ω pi ) is calculated. The energy density in these electrostatic oscillations can amount to 1% of the therm al energy. The presence of high frequency oscillations (ω ~ ω pe ) is concluded from satellites near ± ω pe from the unperturbed line position.

Some types of standing r. f. waves are compared and discussed. As a result a new type of a non-sinusoidal standing wave is proposed which leads to an improved inductive acceleration system. Plasma velocity measurements have been carried out on this system. Numerical calculations are made for the plasma acceleration process and compared with the experimental values of the velocity. The theory as well as the advantage of the proposed system is verified by the results.

Use of microscopic detail in random walk theory describing the initial formations of a large number of avalanches show that concomitant electron transport coefficients quickly relax to equilibrium values. This enables the use of random walks having step sizes and probabilities based only on local electric field strengths and densities. A self-consistent avalanche solution which accounts for collective long range Coulomb interactions as well as short range elastic and inelastic collisions between electrons and background atoms is demonstrated for helium. Avalanche growth retardation followed by an abrupt growth augmentation as time proceeds is shown to be associated with the formation of regions of charge density extrema near the avalanche axis and within the axial distance covered by the electron swarm.

The cooperative problem for a lattice gas on a plane, square lattice and on a simple cubic lattice is solved by a system of two coupled, transcendental equations, derived by a combinatorial method, which describes a homogeneous or periodical particle density on the lattice as a function of the temperature and the chemical potential of the lattice-gas. For the particle interaction a Hard-Core potential (nearest neighbour exclusion) with a soft long-range tail is assumed. The zero-component of the Fourier-transform of this long-range interaction part can be positive or negative. The system of transcendental equations is solved by a graphic method. As a result, the complete pressure-density state diagram and the pressure-temperature phase diagram can be drawn. The lattice-gas exists in three stable phases: gas, liquid and solid. Three phase changes are possible: condensation, crystallization and sublimation. Critical points of condensation and freezing are examined. The number of possible phases and phase changes at a fixed temperature depends on the geometric structure of the particle interaction.

A preceding paper was concerned with the principles of a wave propagation experiment. These appeared suitable for a simultaneous determination of electron concentration N e and of electron collision frequency v in a magnetoplasma. They considered measurements of the refractive index n and of wave polarization ϱ, both of which being determined by field strength ratios. In this paper supplementary numerical calculations are carried out using a plasma model that corresponds to conditions observable in the earth’s lower day time ionosphere and that is characterized by exclusively positive gradients of N e . Furthermore, a modification of the original principle is discussed renouncing measurements of n and using only those of ϱ. Numerical calculations on error propagation demonstrate a significant superiority of the modified version. WKB solutions of coupled wave equations are used. As the plasma model includes local variations of the plasma parameters, the theory can be applied only to limited height and frequency intervals. These are deduced from the coupling parameter Ψ.

To gain information about the nature of the microenvironment of tryptophane residues in proteins, the absorption and fluorescence spectra of such model compounds as indole,- 1,2-dimethylindole, and 2-phenylindole were examined in n-heptane -n-butanol mixtures at different temperatures (20, 80 and 120 °C ). Anomalously large red shifts in the fluorescence bands of these compounds at different n-butanol concentrations in n-heptane indicate that the added n-butanol molecules are concentrated around the solute molecules by electrostatic interactions. The red shift is due to the marked increase in the dipole moment of the excited state and to the number of n-butanol molecules in the solvent shell which can reorient themselves during the lifetime of the excited state of the solute molecule. From the spectroscopic data, making use of the “solvent-shift” theory and the statistical model of Mazurenko, the effective dielectric constant of the microenvironment, the average degree of filling up the solvent shell with n-butanol molecules, the average coordination number and the average interaction energy of the solute with the solvent molecules in the ground and excited state, were calculated.

The centrifugal distortion constants for were calculated using Dowling and Watson’s formalisms. From the fitting analysis and the deviation of predicted transitions it is concluded that the second formalism must be adopted. For the different parameters we have: A′ = 12406.012 ± 0.005 MHz; B′ = 5244.456 ± 0.002 MHz; C′ = 3869.191 ± 0.002 MHz; d J = - 2.08 ± 0 .05 kHz; d J K = -23.63 ± 0.95 kHz; d K = - 33.43 ± 1.69 kHz; d W J = (0.56 ± 0.01) X 10 -6 ; d WK = (5.08 ± 0.22) X 10 -6 .

A conductor has been prepared, consisting of Niobium and an outer layer of the A15-phase Nb-Al and Nb-Al-Ge respectively. The process involves two steps: Coating of Niobium by hotdipping and subsequent heat treatment. The procedure, the products of reaction and data on the transition temperature T c and the critical current density J c of the A15-phase are reported. The maximum values obtained for T c and J c are 18.5 K (19.3 K) and 5 · 10 4 A/cm 2 (2 · 10 4 A/cm 2 ) at 5 T and 4.2 K for Nb 3 Al (Nb 3 Al, Ge).

Using the augmented-plane-wave (APW) method the electronic structure of stoichiometric vanadium carbide has been computed previously 1 . Since only nonstoichiometric cubic phases of vanadium carbide are stable and all experiments are made with such samples, the energy bands have been determined for some nonstoichiometric VC x ; phases (x = 0.87; 0.833; 0.79; 0.75) using the APW virtual crystal (VCA) approximation similar to Schoen’s work on TiO 7, 10 . Our approach differs from his in two aspects: First, the potential is constructed from the self consistent potential of Ref. 1 instead of using atomic data. Thus, the important self consistent procedure is taken into account at least in an approximated form. Second, a more realistic scheme for occupying the states is suggested. Furthermore, an attempt is made to normalize the wave functions in order to obtain the charge distribution in the crystal. The density of states and the partial densities of states corresponding to the quantum numbers n and l have been computed using an LCAO interpolation scheme. The different VC x phases show a fairly “rigid band structure” . The Fermi energy and the density of states at the Fermi level increase with decreasing carbon content. The calculated APW- as well as the LCAO-charge distribution indicate -in accordance with ESCA measurements 32 -that the charge-transfer from vanadium to carbon and the ionicity of VC x decrease with increasing vacancy concentration. The results of X-ray-emission and heat capacity measurements are discussed in terms of the APW-VCA results. Especially for the X-ray-emission data the agreement between theory and experiment is fair.

In a magnetic field a nematic liquid crystal may sustain a variety of twist modes. Their influence upon light propagating trough the liquid crystal can be used to evaluate the twist elastic constant from simple reflection or transmission measurements.

For the same redox ion, diffusion controlled currents have been compared which were obtained at organic crystals and at a gold electrode. These experiments yield quantitative proof for electrochemical saturation currents in organic crystals with electrolytic contacts. Essential for this result is a modified voltage step method which enables an application of a high voltage simultaneous with the first contact between the crystal surface and the charge injecting electrolyte. The conditions necessary for the occurrence of a saturation current are discussed which also determine the electrochemical nature of this current corresponding to an ideal non-equilibrium between redox system and organic crystal.

The kinetics of the reaction between has been studied under conditions of production of iodine at a known rate by the persulfate-iodide reaction and its consumption by S 2 O 3 -- . The effective concentration of iodine during the steady state is measured from its reduction potential at a bright platinum foil electrode. The reaction is of first order with respect to I 3 - and S 2 O 3 -- individually and hence of over all second order. The specific rate is 1.51 X 10 5 M -1 sec -1 and the frequency factor is 1.69 × 10 12 M -1 sec -1 at 25 °C. The energy of activation for the reaction is 9.58 × 10 3 cal/mole and the entropy of activation is -2.55 cal/mole deg.

Phenomenological and physical aspects of the intrinsic tail spectra of the alkalihalides are studied referring to the new results on the intrinsic tail spectra of KBr and KI and to the temperature dependences of the lowest-energy Γ-exciton peak of the sodium- and potassium-halides. Systematically analysing the temperature dependence of the steepness parameter σ s (T) of the Urbach rule for these halides, it is found that the frequency factor has the value nearly equal to the acoustic phonon energy at X or L of each host lattice and the steepness constant σ s0 becomes larger in passing from fluoride to iodide. This halogen dependence of σ s0 is discussed in terms of the hole band-mass of the Γ 8 -level.

An electron microscope imaging method is described which makes use of an electrostatic device, analogous in function to the absorbing phase plate of light microscope, to produce strong contrast in biological specimens. This device is situated at the back focal plane of the objective lens in place of a normal objective aperture. The images created provide an especially realistic representation of the specimen structure and contain information about it that would not necessarily be able to be detected by the conventional bright field method of observation.

An investigation of the microwave spectra of ethyl cyanide CH 3 CH 2 CN and the isotopes CH 2 DCH 2 CN, CH 3 CD 2 CN was carried out. The ground vibrational state of CH 3 CH 2 CN was reexamined under high resolution to give three centrifugal distortion constants D J , D JK and D K . From the rotational constants of the ground vibrational state of CH 3 CH 2 CN, CH 3 CD 2 CN, CH 2 DCH 2 CN (symmetric) and CH 2 DCH 2 CN (asymmetric), CH 3 CH 2 13 CN and CD 3 CHDCN a r 0 -structure is derived. For the isotopes CH 3 CD 2 CN, CH 2 DCH 2 CN (symmetric) and CH 2 DCH 2 CN (asymmetric) the diagonal elements Χ aa , Χ bb and Χ cc of the quadrupole tensor with respect to the principal axes of inertia were deduced from the hyperfine structure of the rotational lines. The off-diagonal element Χ ab for CH 3 CD 2 CN and CH 2 DCH 2 CN (symmetric) and the principal elements Χ zz , Χ xx of the quadrupole coupling tensor were obtained from Χ aa , Χ bb of the two molecules and from the principal axis rotation angle about the c-axis produced by isotopic substitution. For the analysis of the rotational spectra in the first excited states of methyl torsion and the lowest frequency in plane bending vibration of normal ethyl cyanide a molecular model with two internal degrees of freedom is considered. From the rotational line splittings in both states the coefficients V 3 and V 6 of the Fourier expansion of the potential hindering the internal rotation of the methyl group are determined.