Table of contents

We have constructed a new Quantum Nonlinear Schrödinger type periodic chain in which the interaction is long-range and not the usual nearest neighbour one. Using a new form of the transfer matrix with inhomogeneities at the lattice sites a long range Hamiltonian and its eigenvalues are extracted by using the algebraic Bethe ansatz.

Some general properties of the relativistic p-dimensional surface embedded into D-dimensional spacetime and its reduction to the simplest case of the quadratic Lagrangian (the linearized model) are considered. The solutions of the equations of motion of the linearized model for the p-brane with arbitrary topology and massless eigenstates, as well as with critical dimension after quantization are presented. Some generalizations for the supermembrane are discussed.

New observations of the spectrum of Ne-like titanium, Ti XIII, in the region 17–552 Å together with previously reported data have been used in an extended study of the Ti XIII term system. The levels of the excited configurations 2s²2p⁵3s, 3p, 3d, 4s, 4p, 4d, 4f, 5d, 5f, 5g, 6g and 6h are reported. Most of the levels were established from the observations, while some were derived from energy parameters fitted to the observed levels. Observation of the hydrogenic levels has enabled a determination of the ionization energy by means of the polarization formula. The ionization energy is 6 353 000 ± 300 cm⁻¹.

Photoionization cross sections of the main line and shake-up satellites of the outermost inner shell electrons for lithium, sodium and potassium atoms in the ground state and the first excited state are calculated. A relaxed Hartree-Fock approach within the dipole approximation is applied. Large deviations of cross sections of some terms calculated with the term dependent one-electron radial orbitals from those of the average of configuration are found. A strong enhancement of relative intensity of the shake-up satellites to the main line of photoionization from the outermost closed shell for the atoms in the excited state as compared to the similar process for the atoms in the ground state is also found.

On the basis of a semi-classical theory, the rate coefficients of collisional H – H^*(n) ionization and recombination during electron scattering on H – H⁺ complexes and H₂⁺ ions were determined in this paper. The calculations were carried out in the case of non-equilibrium hydrogen plasma with atomic temperature T_a and electronic temperature T_e, in the domains 2000 K ⩽ T_a ⩽ 10 000 K and 2000 K ⩽ T_e ⩽ 30 000 K, with the principal quantum number 4 ⩽ n ⩽ 10. In the paper we have also determined the conditions under which these processes are important for the kinetics of weakly ionized hydrogen plasma.

Beam-foil measurements of the transition probabilities of 2p⁶¹S₀-2p⁵3s ^1,3P₁^o resonance and intercombination transitions in the Ne isoelectronic sequence have been made for elements Na through S. Evaluational problems arise from the multitude of n = 3 levels cascading into the levels of interest. A cascade model permits reproduction of the experimental decay curves and provides guidance for obtaining reasonable lifetime results from multi-exponential fits for the singlet level in Na II through P VI and the triplet level in P VI and S VII. The results corroborate recent theoretical work, but are at variance with some other experimental data for S VII and Cl VIII singlet levels.

The spark spectrum of gold was photographed in the 540–2080 Å region on 10.7 m and 3 m normal incidence spectrographs. The number of classified lines for Au III was increased from 295 to 1040 and 134 new levels were added to the 62 levels of the early analysis. They belong to the doubly excited configurations 5d⁷6s² and 5d⁷6s6p and to the mixed group 5d⁸(6d + 7s). Parametric calculations satisfactorily explain the experimental energies. Theoretical transition probabilities are reported for selected strong transitions.

The XUV spectra from laser-produced germanium plasma are investigated. The energy levels of the 2s²2p⁵3l and 2s2p⁶3l states with l = 0, 1, 2 and the oscillator strengths for the transitions between these levels are calculated by the relativistic configuration-interaction (RCI) method. A high-resolution (λ/Δλ ~ 16 000) grazing-incidence spectrometer is used to measure the spectra in 185–300 Å. The wavelengths of the five lasing lines in Ne-like Ge and the wavelengths of the nonlasing lines have been determined with ±0.04 Å accuracy. The observed lines are assigned to the 3–3 transitions in Ne-like and Na-like Ge ions. The energies of the excited states in Ne-like Ge ions derived from the spectroscopic measurements are compared with the RCI and other theoretical calculations.

The hypothesis of a non-zero divergence of the electric field in vacuo and an associated extended Lorentz invariant formulation of Maxwell's equations provide steady-state solutions of the electromagnetic field. Among the solutions there are those of axisymmetric configurations having integrated field quantities which represent an equivalent electric charge q₀, magnetic moment M₀, mass m₀, and angular momentum s₀. All these quantities become finite and non-zero, at the same time as the corresponding characteristic radius can be allowed to shrink indefinitely, to correspond to the property of a "point charge". The present theoretical model includes relevant quantum conditions, and a condition of equipartition between electric and magnetic energy.

The question is raised whether the obtained results could have a bearing on the physics of charged leptons, such as the electron. In comparison with observed electron data, the present approach thus yields correct signs of the quantities q₀, M₀, m₀ and s₀, the ratio M₀m₀/q₀s₀ is predicted to be of the order of unity as for measured data, a "point charge" of very small radial extension can be obtained, and a minimum charge |q₀| ≅ 1.60 × 10⁻¹⁹ Coulomb is deduced from a simple iteration process, thereby differing at most by about one percent from the measured value of the electronic charge. This suggests that the electronic charge is not an independent constant of nature, but is a typical quantum number determined by the speed of light and Planck's constant. The present theory also fits the muon data, at least within one percent accuracy.

With the magnetohydrodynamic method, the breakdown process in a microdischarge of the Dielectric Barrier Discharge is analyzed. A theoretical model is established to simulate a microdischarge on the basis of the properties of the microdischarge and the effect of the dielectric. Several equations are developed to depict the formation and evolution of the microscopic parameters in a single microdischarge. Some results about the relationships among electron density, electric current density, the property of the working gas and the device configuration have been reached and compared with experimental data.

The kink dynamics in sine and double sine-lattices are considered. We derive the Peierls-Nabarro (PN) barriers, the mobility and diffusion constant of kink. The numerical values of the PN barriers for domain walls in magnetic compounds and for open states in DNA macromolecule are calculated.

The ground state geometries are calculated for fcc clusters with n ⩽ 100 and for icosahedral clusters with n ⩽ 77. The optimization is done by simulated annealing method. Only s-electrons are included in the Hückel model and the lattice relaxation is neglected. The Hückel model and the effective medium theory lead to different ground state geometries. The ground states favour icosahedral structure when 18 ⩽ n ⩽ 30 and fcc lattice structure when 41 ⩽ n ⩽ 77.

Experimental results from a series of investigations, the aim of which is to provide an exploratory overview of the wide range of phenomenon associated with the interaction of slow very highly charged ions with solids and solid surfaces, are reported. Incident charge state dependencies of secondary electron, x-ray and secondary ion emission are measured. In addition, microscopic studies are performed using an "Atomic Force Microscope" to investigate highly charged ion induced surface defects. The ions, used for these studies, range from O⁷⁺ to Th⁸⁰⁺ and U⁸²⁺ with low incident kinetic energies (~2 eV/amu to 3 keV/amu). As an overall result, enhancements for the low energy secondary electron, sputter ion and photon emission are observed with increasing charge states. X-ray emission spectra are found to be consistent with the formation of so called "hollow" atoms above and at the surface as part of the neutralization processes. Small angle scattering behaviour, under specular reflection conditions, indicate very fast decay processes for the hollow atom, outside the solid surface. The microscopic studies reveal interesting nano-size surface defects caused by single highly charged ion incidence.

The emergence, growth and stabilization of stationary concentration patterns in a continuously fed chemical reaction-diffusion system are studied through numerical simulation of the Lengyel-Epstein model. This model represents a key to understanding the recently obtained Turing structures in the chlorite-iodide-malonic acid system. Using the supply of iodine as a control parameter, the regularity of the hexagonal patterns that develop from the noise inflicted homogeneous steady state is examined. In the region where they are both stable, the competition between Hopf oscillations and Turing stripes is studied by following the propagation of a front connecting the two modes. Finally, examples are given for the types of structures that can develop when a gradient in feed concentration is applied to the system.

A rank correlation method was applied to investigate the influence of atmospheric thunderstorm conditions on the life time (observation time) of Ball Lightnings (BL). Data from the PC Stakhavov-Keul-Bychkov Data Bank on BL were used. For the analysis a ranking of BL over sizes has been made and a ranking of atmospheric conditions of the BL observations in respect to humidity and of thunderstorm conditions in respect to electric field strength of the atmosphere ground layer have been made. Statistical analysis reveals that both the increase of the humidity and of the electric field strength decreases the BL life time. These results are discussed from the point of view of the different BL models.

The initial of the fourth author is M and not H as appeared in the published article (1995 Physica Scripta52 588).