Table of contents

The nonlinear dynamics of a one-dimensional two-sublattice model for a discrete inhomogeneous hydrogen-bonded chain is investigated in the low-velocity regime. We use the reduced Lagrangian approach to derive an effective equation of motion for the centre of mass of a single "distorted" two-component soliton. The system dynamics on the phase plane is analysed for special cases making use of the energy-conservation principle. The two-component soliton interaction (reflection and capture processes) with impurities depends on the lattice discreteness. Numerical estimations of threshold velocities and oscillatory frequencies have been performed for ice.

Discovered effectively two decades ago, the "rotospheres" (or also the regions "in a pre-horizon regime") around collapsed relativistic sources have been analyzed thoroughly (and given their name) just lately. So far only those specified by the unusual behaviour of acceleration of the observer in azimuthal motion have been considered. Here I find, in Kerr spacetimes, the rotospheres defined with respect to latitudinal motion.

Dynamics of structure formation and structure transitions in media with and without wave motions are considered. It is shown that the development of weak secondary instabilities of mature ideal dissipative structure causes the appearance of imperfect patterns with distributed defects. The perfect and final imperfect patterns are described by the same value of the structure intensity. When the structural transition takes place (as a result of stronger secondary instability), every quasi-steady and final steady states has a different value of the structure intensity.

Energy levels in ⁴²Ca have been studied by means of the three-particle transfer reaction ³⁹K(α,p)⁴²Ca. Angular distributions of the emerging protons have been measured in a multigap magnetic spectrograph. Theoretical cross sections have been calculated using both a microscopic and a semi-microscopic model.

Lifetime measurements are reported for several levels in the 2s2p3p, 2s2p3d, 2s2p², 2p³ configurations of boronlike N III. Beam-foil excitation methods were used with cascade repopulation analyzed by the correlated decay curve ANDC technique. A small but significant J-dependence in the lifetimes of the 3d ⁴F levels was observed. The experimental lifetimes for the levels in the 2s2p² and 2p³ were found to be in good agreement with recent theoretical results.

The collisional broadening and shift of the ¹¹⁴Cd 326.1 nm (5 ¹S₀-5 ³P₁) intercombination line perturbed by Kr have been investigated using a pressure-scanned Fabry-Perot interferometer. The values of pressure broadening and shift coefficients determined from experiment are compared with those calculated on the basis of the classical Lindholm-Foley impact theory for van der Waals, Lennard-Jones, Morse and Czuchaj-Sienkiewicz potentials.

This paper reports an extended experimental investigation, using the beamfoil technique, of the intensity ratio of the fine-structure components in the 3s²3p ²P_1/2,3/2–3s3p²²S_1/2 and ²P_1/2 resonance transitions along the Al I isoelectronic sequence. These intensity ratios are strongly influenced by cancellation/enhancement effects arising from spin-orbit induced level mixings, and are thus sensitive probes of the detailed atomic structure. New data are given for Si II, P III, S IV, K VII, Sc IX, Fe XIV and Ni XVI. Together with previous experimental results this comprehensive isoelectronic study reveals significant and systematic deviations from theoretical predictions.

The spectrum of silver was photographed in the region 500-2000 Å on a variety of normal incidence spectrographs using triggered spark and sliding spark sources. The 4d⁶5s–4d⁶5p transitions of the fifth spectrum of silver were analysed. 59 levels out of 63 levels of the 4d⁶5s configuration have been established. Of the twelve missing levels of the 4d⁶5p configuration seven have been located. 610 additional lines have been classified in the Ag V spectrum. The parametric least-squares-fitting calculations were carried out to interpret the spectrum satisfactorily.

A theoretical study of five odd configurations of singly ionized platinum was performed in the framework of the Slater-Racah theory. This led to the interpretation of all 202 experimentally known energy levels. In the earlier analysis we altered the J-values of five levels and removed the indeterminacies in J-values of another 13 levels. Twenty-eight new levels were found in the vicinity of the predictions, and the lowest levels of 5d⁸7p and 5d⁶6s²6p were identified at 106 995 and 104 625 cm⁻¹, respectively. The transition probabilities computed in the HXR option of the Cowan code are in good agreement with observed intensities of Sansonetti J E, Reader J, Sansonetti C J and Acquista N (1992 J. Res. NIST97, 1). One hundred and fifty-one newly classified lines are reported in the range 1077-4104 Å.

Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consequtive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak.

In the present paper are found the solution of a model-Hamiltonian that describes the three-level two cavity mode Jaynes–Cummings model in Kerr-like media (nondegenerate case). Finally we calculate atom level populations as well as squeezing for the quadrature components of the cavity modes and of the total field.

The effect of moving mass center and Stark shift on atomic dynamics for various initial conditions is studied by the two-photon Jaynes-Cummings model. Our investigations show that, the Doppler effect exercised by the motion of atomic mass-center can lead to the modified phenomenon of oscillation collapse and revival in the transition probability, in the presence of the Stark shift, the period of the oscillation is shorter than that in its absence.

The weakly nonlinear theory of the two-field model of drift wave turbulence is outlined. It was demonstrated within the framework of this model that a double energy cascade is an element of spectral transfer due to the presence of two quadratic invariants and Poisson bracket type nonlinearities. The obtained results are illustrated by two examples of drift wave turbulence known in magnetized and unmagnetized plasmas.

We derive the basic equations for magnetoacoustic hydrodynamics (MAD). A new branch of electromagnetic waves having small damping is obtained in the range of the electron cyclotron frequency in a strong collisional plasma. Filamentational and modulational instabilities are elaborated. The effect of helicon waves (whistlers) on the plasma is considered and instabilities are studied. The formation of solitons and shock waves is investigated.

Polarization spectroscopic effects caused by drift selfalignment of ions drifting slowly in a plasma have been analysed theoretically and observed experimentally. The complex experimental-theoretical approach to a model laboratory gas discharge in a hollow cathode enables us to put forward a new optical method for remote sensing of low drift velocities of ions and the distribution of electric fields in ionized gases of different physical nature.

This study is concerned with measurements of the anisotropic part of the azimuthal component of the ion velocity distribution function by means of a singly gridded ion energy analyser. The experiments are performed at a magnetised plasma column in order to investigate the dependency of the E × B-rotation velocity of the plasma on the radius. The ion velocity distribution function is determined from the numerically differentiated current voltage characteristics of an ion energy analyser. The anisotropic part of the distribution function is found to be proportional to the normalised difference of the derivatives of a pair of characteristics, recorded in up- and downstream direction with respect to the local rotation velocity. The experimental data indicate an ion velocity distribution function, which closely resembles a Maxwellian in a frame moving with the plasma rotation velocity. The measured anisotropic part of the ion velocity distribution function is evaluated applying a procedure that treats the thermal and rotation velocities of the ions as free parameters of a (non-linear) model function and fits them to the experimental data in the ion retarding regime of the characteristics. Furthermore it is shown that in the presence of a moving plasma only the difference of the derivatives of a pair of characteristics indicates the plasma potential. Thus the local radial electric field can be determined and indeed is used to calculate the dependency of the E × B-rotation velocity on the plasma radius. These calculated E × B-rotation velocities agree with those measured by an ion energy analyser within the range of experimental uncertainties, indicating minor influence of the ion pressure gradient on the rotation of the plasma column studied.

The influence on the dynamics of a fusion plasma of a contribution of resistive-ballooning mode turbulence ~T^−1/2 in addition to the temperature gradient driven drift-wave turbulence in the transport coefficients is investigated. For the central part of the plasma the coupled equations for the evolution of temperature and density leads to the results that the high temperature stationary point which is stable, will be lowered as a consequence of the presence of the resistive-ballooning mode transport, whereas the low temperature stationary point which is unstable, and which exists for a bounded plasma in the presence of bremsstrahlung radiation losses, will occur at increased values of the temperature.

A kinetic description of the Ar-Hg plasma in dielectric barrier discharge is given on the basis of establishing a Collisional Radiative Atomic and Molecular Model (CRAM). The population transfers among atoms and excimers are taken into account. A new method to treat the recombination of electrons and ionized particles is developed. The time-dependent model gives us a description of the evolution of the plasma phase performing chemical reactions in a microdischarge and the spectroscopic information on the atomic and molecular radiation as well.

Corrections to Fojón et al 1995 Physica Scripta51 204.