Table of contents

The total cross sections for the near threshold η production in proton-proton collisions has been investigated with the assumption that the production mechanism is due to the emission of a meson x(π,η,σ) from one of the nucleons followed by a xN → ηN transition on the second nucleon. The xN → ηN amplitudes are generated from the unitary multi-channel multi-resonance model which has recently been constructed by fitting the data of πN elastic scattering and πN → ηN reaction. The initial and final pp distortions are calculated from a coupled-channel πNN model which describes the NN scattering data up to about 2 GeV. With the xNN vertex functions taken from the Bonn potential, the predicted total cross sections of threshold pp → ηpp reaction are in good agreement with the data. In contrast to previous works, we find that the η-exchange plays an important role.

The spectrum of osmium was photographed in the 225-2100 Å region on a 3m normal incidence spectrograph using a triggered spark light source.

The (5d⁴ + 5d³6s)−5d³6p transition arrays of Os V were investigated and 703 lines have been classified.

The analysis of the spectrum of Os V has resulted in the determination of 57 levels in the (5d⁴ + 5d³6s) even system and of 89 levels in the 5d³6p odd level system.

The energy levels and their eigenvector compositions have been described by means of the orthogonal operator technique. Three particle electrostatic effects of the ddp-type have been established for the first time in the 5d-elements.

Accurate gA-values calculated by means of orthogonal operators are presented also.

The amplitude for non-resonant photon scattering by an atom or molecule in its ground state is considered in the context of non-relativistic quantum electrodynamics. The forward scattering amplitude has applications to the refractive index of dilute isotropic media, including optically active media. The scattering amplitude, however, exhibits an apparent discontinuity in the forward direction. It is shown that the discontinuity is removed by non-relativistic renormalization of the electron mass.

A double-layer interferometer containing a sodium atomic vapour and irradiated by white light produces in the focal plane of a concave diffraction-grating spectrograph a set of concentric elliptic rings of equal chromatic order (RECO) that are crossed by the absorption D-line of Na atoms. The RECOs are strongly distorted in the close vicinity of the spectral components of the D-line. A comparison of the perturbed and the unperturbed RECOs yields a dispersion curve that is fitted to the Sellmeier function to find the level population whose dependence on the vapour temperature and/or pressure is found to exhibit an exponential growth.

A double-layer interferometer containing a flame-excited vapour of sodium atoms is irradiated by a continuous-spectrum source. Light transmitted by this interferometer is resolved by a prism spectrograph of moderate resolution where a set of concentric rings of equal chromatic order (RECO) replaces the continuous spectrum of the background source. The elliptic RECOs are perturbed as they are being crossed by the absorption D-line of Na. The RECO perturbation is measured so as to construct the dispersion curve in the extended wings of the absorption line. The obtained results are fitted to a modified Sellmeier dispersion function to deduce the level population due to the flame excitation of Na atoms.

We have developed asymptotically correct electron wavefunctions and densities in isolectronic sequences of inert-gas atoms, based on asymptotically correct, equivalent potentials. They allow us to obtain reliable values for ⟨rⁿ⟩. We use these expectation values to obtain a universal function to describe high-energy e-inert gas atom scattering. Experimental data are found to conform to this description.

Spectral line shapes of ions in hot plasmas submitted to a strong oscillating electric field have been theoretically studied by applying standard hypotheses of plasma line broadening along with a nonperturbative (Floquet) treatment of the (external) oscillating field. The formulation has been applied to the two first resonance lines of various hydrogenic ions in hot plasmas subjected to a strong Langmuir oscillation or submitted to an intense laser field. It is shown that the simultaneous action of a strong oscillating field and the plasma particle fields can lead to large modifications of the spectral line shapes.

The paper considers the conditions for sustaining low-pressure plasma columns by travelling electromagnetic waves in symmetric and dipolar modes, respectively. The treatment is fully electrodynamic. It is shown that the wave energy flux along the plasma column determines the conditions for sustaining the discharge. In particular as the plasma is sustained by a symmetric wave whose flux depends mainly on the radial distribution of the wave electric field whilst for a dipolar wave sustained plasma the flux is specified by the magnitude of the axial wave field component at the plasma-dielectric interface.

Electromagnetic waves in a dusty plasma up to frequencies between the ion cyclotron frequency and the cyclotron frequency of the charged dusty grains are investigated. Kinetic Alfvén waves in these and lower ranges of frequency are studied. Physical phenomena based on these waves are discussed.

Using the self-similar solution in the form of the rarefaction wave for the case of non-zero ion temperature, particle and energy transport in the process of plasma expansion into a vacuum is studied. The approach permits the energy distribution of the ions passed through a given plane, their total number and total and averaged energies to be calculated without resort to simulation or other complicated computations. The obtained solutions are found to be in good agreement with the computer simulation data.

A simple model of the Davydov-Zakharov class for laser-produced plasmas is developed. The rarefaction shock waves related to this model include critical steepening, as well as magnetic field generation. The corresponding current densities may reach values of the order 1 kA/μm².

A model has been developed which is capable to describe in a self consistent way the plasma dynamics in the centre and edge region of a fusion reactor. The core plasma is treated in the frame of the 0D model in which an empirical scaling law for the energy confinement time is included. The model accounts for energy losses due to Bremsstrahlung and line radiation as well as alpha particle heating. A 1D analytical model for plasma and impurity transport outside the last close magnetic surface (LCMS) is applied. The model accounts for the strong gradients of the plasma parameters along the magnetic field lines in the divertor. The sputtering phenomena at the plate and radiating cooling by injected impurities are treated self consistently in the model. The model has been used to investigate operating regimes of the ignition experiment. Analysis have been performed for different first wall materials (C, Ni, Mo, W) for ITER like tokamak.

A macroscopic continuum model for optical phonon modes is applied to obtain the planar vibrational modes of a monoatomic layer embedded in a homogeneous material. The differences in optical force constants and reduced masses across the atomic plane are considered within the theory as a fundamental factor to describe the modes localized at the interface. We have derived analytical expressions for the phonon spectrum, as well as for the vector displacement and electric potential as a function of coordinates. An analysis of the infrared and Raman activity for the obtained modes is given together with a comparison with recent experimental data.

The influence of the anisotropy on the phase transitions of an interface layer is investigated by the use of the effective field theory. This interface layer divides the system into two semi-infinite bulks B and B'. Phase diagrams of the interface are given as a function of Δ = (J_x/J) − 1 and α = J_x/J_y where J_x and J_y are the nearest-neighbour exchange constants in the interface. Magnetization curves of interface are given as functions of the temperature for some values of α, Δ and α' = J'/J where J(J') is the exchange constant in the bulk B(B'). Only the cases in which Δ ⩾ 0 and α ⩽ 1 are considered in this work.