Zum Einfluß der Energieabhängigkeit der Elektronenstoßfrequenz auf die elektrische Leitfähigkeit schwach ionisierter Plasmen

With regard to experimental applications in plasma diagnostics numerical approximations are given for the Gurevic-type correction functions, which in the kinetic theory of weakly ionized plasmas describe the deviations from the Lorentzian electrical conductivity. The approximations are based either upon the dependance of the collision frequency on the power of the electron velocity, or on a first order Taylor expansion around the most probable electron velocity of a Maxwellian distribution. For all assumptions regarding the velocity dependance of the collision frequency the influence of temperature (and pressure) on the effective collision frequency is indicated.     

Berechnung der Zustandsdichte ungeordneter Legierungen mit starker Elektronenkorrelation

Calculation of the Density of States of Disordered Alloys with Strong Electron Correlation A method is derived, which is a generalization of the coherent potential approximation. Herein the electron correlation is considered using a simple approximation (alloy analogy). The equation for the coherent potential can be reduced to a real equation of 5-th order. The main advantage of the method is the exclusively simple possibility for numerical analysis.     

Allgemeine Berechnung der Elektronenverteilungsfunktion von schwach ionisierten Plasmen in beliebig zeitabhängigen elektromagnetischen Feldern

The behaviour of a weakly ionized plasma in external, arbitrarily time-dependent, electromagnetic fields is treated within the framework of kinetic theory. The Boltzmann kinetic equation is solved using the Lorentz ansatz, taking into account elastic collisions between electrons and neutral particles and assuming that the collision frequency is independent of the electron velocity. The drift velocity of electrons enters into the isotropic part f₀ and into the direction-dependent part f₁ of the electron distribution function. A method is given for the calculation of the drift velocity, which is calculated explicitly for the important but difficult case of a sinusoidal electric field in the presence of a magnetic switching field. f₀ and f₁ are calculated; f₀ is investigated generally. f₀ consists of an expansion in generalized Laguerre polynomials. The influence of the electromagnetic fields on the distribution function and its time variation is discussed and the relaxation behaviour is shown. The following two special cases are calculated explicitly: a linear rising electric field and a sinusoidal electric field, both in the presence of a constant magnetic field.     

Berechnung der Amplitudenfluktuation eines mit Laserlicht gepumpten optischen parametrischen Oszillators

The intensity fluctuations of the radiation of an optical parametric oscillator have been calculated by taking into account the corresponding fluctuations of the pump light. The latter are shown to have a strong influence on the fluctuations of signal and idler waves. In contrary to the laser case, they are essentially reproduced in the signal and idler radiation; more quantitatively, the correlation function 〈?(t₁) ?(t₂)〉 where ? denotes the deviation of the amplitude of the signal (or idler) wave from its mean value is, for t₁ = t₂, equal to the corresponding quantity for the pump wave apart from a reduction factor, whose value depends on the resonator losses and the relative excitation of both the pumping laser and the optical parametric oscillator and is found to be of the order of one for the normal case. It is interesting to note that for sufficiently strong pumping, the correlation function 〈?(t₁) ?(t₂)〉 approaches the value zero for |t₁ – t₂| → ∞ not monotonically but in form of damped oscillations.     

Berechnung der Energieverluste schneller Elektronen in dünnen Schichten mit Retardierung

Regarding the retardation of the electromagnetic field, a semiclassical formula for the energy-loss-probability of fast electrons penetrating a thin foil with a dielectric constant?=?(Ω) is derived. This formula is discussed for the special cases of the free electron gas and the occurence of Cerenkov-radiation in substances with high dielectric constants. Numerical evaluations have been made for these cases. Significant deviations from the formula without retardation are found, which are confirmed by the experiments.     

Bestimmung der Abschirmung der magnetischen Kernresonanz und der magnetischen Suszeptibilität durch Berechnung der Stromdichte diamagnetischer Moleküle mit der Methode der finiten Elemente

Determination of the NMR-Shielding and of Magnetic Susceptibility by Calculation of the Current Density of Diamagnetic Molecules by the Finite Element Method In paper [20] the finite element method was initiated for calculations of diamagnetic properties of molecules on the basis of a semiclassical approach [18, 19]. In the present work this method is used in the frame of the uncoupled Hartree-Fock-perturbation theory. It is shown that the proposed approach is applicable to localized orbitals, the susceptibility and the shielding being divided into incrementary contributions. Furthermore the relationship to the semiclassical approach and to the approach of Rebane [7] is shown. The H₂-molecule, the threedimensional anisotropic harmonic oscillator and the CH₄-molecule serve as examples to present the possibilities of this method.