Table of contents

Atomic lifetime measurements yield information on atomic wavefunctions that supplements the data from atomic energy levels, but is more sensitive to details of the radial wavefunctions. Transition rates of intercombination (spin-changing) and electric-dipole forbidden transitions are of interest also for applications in plasma diagnostics and astrophysics. Earlier lifetime measurements of low-charge state ions in radiofrequency, electrostatic and Penning ion traps have recently been supplemented and in some cases superseded by experiments on electron-beam ion traps (EBIT) and heavy-ion storage rings. Several of these measurements of lifetimes in the range from 10 µs to 500 ms have reached uncertainties of better than 0.5% and challenge theory. Typical features of ion trap experiments, performance problems and technical developments are reviewed, and likely routes of further progress are outlined.

It is shown that the Maxwell–Heaviside theory is incomplete and limited, for example, it is unable to describe the Sagnac effect, either with platform at rest or in motion. An electrodynamical theory based on a physical internal O(3) gauge space is shown to provide the correct explanation in classical electrodynamics for the Sagnac effect, and for interferometry in general, for example Sagnac and Michelson interferometry. The U(1) sector of unified field theory must therefore be replaced by an SU(2) sector broken to O(3). This has numerous consequences for unified field theory.

A galilean description of rotations is generally used to analyse this old problem. This implies a breakdown of the relativistic covariance of electromagnetism which is a possible cause of discrepancy between theory and experiment. In this work, we use a relativistic description of rotations that restores the full covariance of Maxwell's equations to analyse the radiation due to a dielectric sphere rotating in a static electric and magnetic field.

A simple model of a two-mode non-resonant parametric amplifier is studied with special regard to non-classical features such as revivals and squeezing. The methods used apply for an arbitrary pump parameter. Detailed analytical and explicit expressions are given when the coupling of the two modes has a harmonic time-dependence. Despite its simplicity the model exhibits a very broad range of intricate physical effects. We show that quantum revivals are possible for a broad continuous range of physical parameters in the case of initial Fock states. For coherent states we find that such revivals are possible only for certain discrete rational number combinations of the ratio of frequency detuning and pump parameters. Correlation effects are shown to be very sensitive to the initial state of the system.

Chern-Simons couplings between Yang-Mills gauge fields and an abelian 2-form are derived by means of cohomological arguments.

We have analyzed the direct photon data obtained by the WA80 collaboration in 200 A GeV S+Au collision at CERN SPS, in a one dimensional hydrodynamical model. Two scenarios were considered: (i) formation of quark-gluon plasma and (ii) formation of hot hadronic gas. For both the scenarios, ideal as well as extremely viscous fluid was considered. It was found that direct photon yield from QGP is not affected much whether the fluid is treated as ideal or extremely viscous. The yield however differ substantially if hadron gas is produced. None of the scenarios gives satisfactory description of the data.

New experimental data are discussed on the distribution of protons over transverse momentum of p⊥ in the Fe + Em process at energies 2–200 GeV/n and of α-particles in the Au + Em process at incident energy 10.7 GeV/n. A possible interpretation of the experiment within the framework of the gluon dominance and the thermodynamic approximation can be achieved with a minor additional assumption only. This assumption is that at an early stage of evolution of the heavy baryon cluster matter the quark matter transforms into baryons at a temperature T ≈ 0.22 GeV and its global decay into nucleons is completed at T ≈ 0.14 GeV. The results are also of interest in connection with the problem of abundance of helium and hydrogen in the universe which has been considered in cosmology and astrophysics for a long time.

Using a semiclassical approach, we have calculated electron-, proton-, and He III-impact line widths and shifts for 2 F VI, 10 Cl VII and 6 Kr VIII multiplets, as a function of temperature.

A new set of transition probabilities is derived for many transitions of Ce II of astrophysical interest. A relativistic Hartree-Fock method, combined with a least-squares fitting of the available experimental levels, including a number of newly determined values, has been used for the determination of the eigenfunctions and eigenvalues. Configuration interaction and core-polarization effects have been introduced in the calculations. The derived oscillator strengths lead to a new value of the cerium abundance in the solar photosphere, A_Ce = 1.70 ± 0.04 (in the usual logarithmic scale) which is somewhat larger but in reasonable agreement with the meteoritic result.

Heavy ion induced inner shell ionization produces multiple vacancies in the outer shells (M, N etc.) simultaneous to vacancies in the inner-shells (viz. L-shell), which in turn create a very complicated electronic configuration. Three projectiles N^2+,3+, Si^7+,8+ and Ti^10+,11+ ion beams having a range of 0.3 to 3.5 MeV/u were bombarded on a thin rare earth target of Yb. The recorded L x-ray spectra of Yb have been analyzed in the light of multiple ionization produced due to the heavy ion impact. The outer-shell vacancies acting as spectator vacancies cause a shift in the energy of the various emitted L x-ray diagram lines. A comparison of the shifts in the energies of the various L x-ray transitions of Yb due to the impact of these projectiles, from standard values and that due to proton impact along with the deviation of the intensity ratios from single hole branching ratios, reveal a dependence of multiple ionization on the projectile atomic number (Z) and energy. A further comparison of the degree of multiple ionization produced in Yb, evident by the number of spectator vacancies produced due to the impact of projectiles with 7 ≤ Z ≤ 22 and overlapping MeV/u range lead to explicit conclusions regarding the probability of multiple vacancy production in outer shells simultaneous to a single L-shell vacancy for such projectile target combinations.

In this paper a single-degree of freedom system with quadratic and cubic nonlinearities to an amplitude-modulated excitation whose carrier frequency is much higher than the natural frequency of the system is investigated by the multiple time scales perturbation technique [MTSPT]. The perturbation analysis is used to obtain a second order nonlinear equation governing the low-frequency response of the system. The response of the system to (constant) unmodulated and (harmonically) modulated excitations is investigated. Numerical investigations are given to study the effects of various parameters on the stability of the system response.

The object of the present work is to study the effects of Hall and ion-slip currents on free convection flow past a semi-infinite vertical flat plate for the case of a strong magnetic field imposed perpendicularly to the plate. The effect of internal heat generation or absorption is also considered. The derived fundamental equations on the assumption of small magnetic Reynolds number are solved numerically. The velocity profiles, temperature profiles, the skin friction components on the plate and heat transfer coefficient are computed and discussed in detail for various values of the magnetic field parameter, Hall parameter, ion-slip parameter and heat source/sink parameter.

The paper presents equations of motion for two-phase flow based on the diffuse-interface method. Two cases are considered: the non-ideal fluid and the binary fluid. In the binary-fluid case, it is shown that the equation obeyed by the concentration is more general than the one which is usually postulated. Averaged equations are deduced for both cases.

A fully nonlinear analysis has revealed large amplitude ion acoustic compressive solitary waves beyond the predicted limit (Δ < 3) (Goswami B N and Buti B 1976 Phys. Lett. A 57 149) of K-dV equation. In a hot electron dominated plasma, dispersion of a compressive solitary wave is found to increase with increasing T_h which bounds thee corresponding solution by some minimum value of cold to hot electron temperature ratio.

Within the context of the general theory of low-frequency electromagnetic plasma fluctuations, the stationary spectra of short-wave convective and magnetostatic perturbations and the heat conductivity coefficient in finite-pressure plasma with β_e ~ β_i ~ 1, are obtained. It is shown that the nonlinear broadening of the potential spectrum can be determined by the magnetic field fluctuations when β_e ~ 1. In this case, the renormalized damping coefficients display cubic k-dependence and do not keep logarithmic corrections, whereas the anomalous heat conductivity is essentially reduced.

A low-frequency magnetomechanical oscillatory response of a nematic liquid crystal with positive diamagnetic anisotropy is studied whose reactive force is dominated by antisymmetric stresses originating from magnetic polarizability of nematic soft matter. It is found that a uniformly magnetized nematic matter possesses capability of transmitting a transverse magneto-torsion wave in which the velocity of vortical flow and director undergo coupled oscillations in the plane perpendicular to the axis of magnetization and traveling along the applied magnetic field. The dispersion equation characterizing propagation of this wave is obtained, followed by a brief discussion of possible experimental identification of the magnetotorsion mode.

The role of the finite collision duration in high electric fields is examined for its effect on the scattering rate relevant in many submicron and nanoscale semiconductor devices. Starting from a general non-linear quantum transport equation, an approximate high field quantum kinetic equation is derived, which can be viewed as the first step towards a quantum Boltzmann equation. Based on this equation, the high field scattering rate of electrons is calculated for GaAs in the case of optical phonon scattering at room temperature.

The random field Ising model with four spin interactions is studied within the finite cluster approximation (F.C.A), on square and simple cubic lattices. We have investigated the influence of the four spin interactions on the phase diagrams of the system. We have shown that for the simple cubic lattice, the tricritical behaviour due to the random field does not exist for every strength of the four spin interactions, and that he tricritical point due to four spin intenactions disappears when the value of the random field is large.

The optimization of Bragg-confined double quantum wells with respect to resonant second harmonic generation and electro-optic coefficients is considered. The method of optimization relies on solving a system of nonlinear equations which involve the geometric parameters of the structure and bound state energies. Advantage is taken of the above-the-barrier bound states in Bragg-confined structures, in order to extend the range of allowable incident photon energies. Numerical results are given for Al_0.48In_0.52As/Ga_0.47In_0.53As based structure and the incident photon energy ℏω = 240 meV.