Table of contents

By using an asymptotic expansion technique based on the Lagrangian density formulation, it is demonstrated that the nonlinear interaction between two transverse waves propagating in a generalized elastic solid is described asymptotically by the complex modified Korteweg–deVries (CMKdV) equation. Also, the CMKdV equation is shown to be Hamiltonian and its solitary wave solutions are investigated by means of a modified Hirota method.

A three-channel, multi-resonance, unitary model developed in 1995 is used to determine the πN → ηN and ηN → ηN amplitudes by re-analyzing the available data on πN elastic scattering and the weighted data for the πN → ηN total and differential cross sections. The input πN elastic scattering amplitude in the S₁₁ channel has been improved, following suggestions of G. Höhler. Our new result of ηN scattering length, a_ηN = (0.717±0.030)+i· (0.263±0.025) fm, suggests that the ηd system is unbound or loosely bound.

A detailed analysis of the x-ray spectrum emitted by a laser-produced plasma of barium in the 8–13.5Å wavelength range is given. The plasma is produced by the irradiation of an ultra-short pulse laser on a BaF₂ target. Ab-initio calculations using the RELAC relativistic computer code are performed to identify 3d–nf (n = 4 to 8), 3p–4s, and 3p–4d transitions of Ni-like Ba XXIX, and corresponding satellite transitions in neighbouring ionization states: Fe-, Co-, Cu-. Zn-, Ga- and Ge-like ions. By changing the focusing conditions of the laser pulse on the solid target, one can get different ionization charge distributions and resolve some ambiguous identifications.

Destabilization of atomic anions is studied for the ground ¹S and first excited state ³P of the ten-electron system. Using large and diffuse basis sets, configuration-interaction calculations show that for decreasing nuclear charge Z the ground state ¹S is absorbed into the continuous spectrum at the critical parameter value Z_c(¹S) ≈ 8.74 e₀, and the triplet state at Z_c(³P) = 9 e₀. This implies instability of the di-anion O^2- and excludes existence of stable excited bound states of F^-. The numerical results give strong evidence of different absorption mechanisms into the continuum for ¹S and ³P, involving zero-energy threshold bound or virtual states, respectively. Arguments from the rigorous theory of Schrödinger operators lead to the expectation that the observed phenomena are manifestations of more universal properties common to all anionic systems.

The spectra of different ions of iridium were photographed on a 3-m normal incidence spectrograph at the Antigonish laboratory in the 300–2100Å wavelength region using a triggered spark source. The 5d³–5d²6p transitions of Ir VII were investigated. All 19 levels of the ground state and 44 out of 45 levels of the 5d²6p configuration have been established. 204 lines have been classified in 375–575Å region. Hartree–Fock (HF) and least-square-fitting (LSF) parametric calculations interpret the observed spectrum satisfactorily.

The spectrum of Au V is investigated in the 475–690Å region, in which the 5d⁷–5d⁶6p transition array is located. In this array 350 lines have been classified. All (19) levels in the 5d⁷ configuration were established. In the 5d⁶6p 115 (180) levels have been determined. Orthogonal operators have been used to fit the experimental level values and to obtain eigenvalues and eigenvector compositions.

In this work it is studied the effect of the choice of the initial electron distribution in collisions with electron transfer between bare nuclei and H atoms, when the electron is in the 2s state, within the Classical Trajectory Monte Carlo (CTMC) method. The standard microcanonical distribution, used to choose an initial electron distribution, is compared with two other distributions: one which reproduces the exact quantum mechanical momentum distribution, and another close to the correct quantal radial distribution. It is seen that the results of the method are not sensitive to the details of the distribution chosen.

Methods for non-parametric regression have been applied for pair lifetime and diameter of Ball Lightnings (BLs) that disappear through explosion, extinction and decay. BLs lifetime increases in case of BL, that disappear through extinction and decay in range of diameters 0.5–100cm. Lifetime of BLs, that disappear through explosion, increases at diameters smaller than 60cm and decreases for greater diameters. Comparison with data on experimentally obtained fire balls and with existing theories was conducted. Polymer BL theory gives a possibility to explain obtained results.

Using a semiclassical approach, we have calculated electron-, proton- and ionized helium-impact line widths and shifts for 66 MgII multiplets as a function of temperature. The results obtained have been compared with available experimental and theoretical results.

A rigorous theoretical investigation has been made of obliquely propagating electrostatic solitary structures in a hot magnetized dusty plasma which consists of a negatively charged, extremely massive, hot, dust fluid and Maxwellian distributed ions and electrons. The reductive perturbation method has been employed to derive the Korteweg–deVries (K–dV) equation which admits a solitary wave solution for small but finite amplitude limit. It has been shown that the effects of dust-temperature, obliqueness, magnetic field and free electrons have changed the nature of the electro-static solitary structures. The result of the present investigation for unmagnetized case, parallel propagation, no free electron and cold dust fluid completely agrees with the existing published results (Mamun et al. [4]).

A study on the extremely low-frequency possible electrostatic modes in a finite temperature magnetized dusty plasma taking the charged dust grains as the third component has been carried out using the appropriate Vlasov-kinetic theory for the dynamics of the electrons, ions and the dust particles. It is found that the inequalities of charge and number density of plasma species, and the finite-Larmor-radius thermal kinetic effects of the mobile charged dust grains, introduce the existence of very low-frequency electrostatic eigenmodes in the three-component homogeneous magnetized dusty plasma. The relevance of the present investigation to space and astrophysical situations as well as laboratory experiments for dust Coulomb crystallization has been pointed out.

Vertical oscillations in the Coulomb chains of dust grains arranged in a vertical chain in a sheath region of a low-temperature gas discharge plasma are investigated. The characteristic frequencies of the modes are found. The number of the modes is equal to the number of particles in the chain.

Low energy photons drive the transitions between trapped electron states in glasses (generate the charge transfer excitons). Orientational ordering of their dipole moments results in positive feedback what allows to design an amplifier of a static electric field.

The region of the existence of the crystal phase in two-layer system of spatially separated electrons (e) and holes (h) in coupled quantum wells at different densities n, temperatures T and interlayer separations D is considered. For analysis of the crystal phase the variational calculation of the energy of the ground state of the system with the account of the pairing between quasiparticles with nonzero momenta is used. Regions in (T, n, D)-space where electron (or hole) charge density waves (CDW) exist in each layer is obtained. These regions contain smaller (T, n, D)-regions where crystallization of indirect excitons (or pairs with spatially separated e and h) takes place (this crystallization corresponds to the existence of electron and hole CDW in-phase).

The transport relaxation time τ(P) and the mean free path of magnetoexcitons in single and coupled quantum wells are calculated (P is the magnetic momentum of the magnetoexciton). We present the results for magnetoexciton scattering in a random field due to (i) quantum well width fluctuations, (ii) composite fluctuations and (iii) ionized impurities. The time τ(P) depends nonmonotonously on P in the case (ii) and in the case (i), (iii) for D/l smaller than some critical value (D is the interwell separation, l = √(ℏc/eH) is the magnetic length). For D/l >> 1 the transport relaxation time increases monotonously with P.

The magnetoexciton mean free path λ(P) has a maximum at in the P ≠ 0 cases (i), (iii). It decreases with increasing D/l. The mean free path calculated for the case (ii) may have two maxima. One of them disappears with the variation of the random fields parameters. The maximum of λ(P) increases with H for types (i, iii) of scattering processes and decreases in the case (ii).