Table of contents

We obtain the low-lying energy-momentum spectrum for the imaginary-time lattice quantum field model associated with d-dimensional lattice ferromagnetic classical N-component vector spin systems at high temperature (0 < β << 1). Each system is characterized by a single site a priori spin probability distribution. The energy-momentum spectrum exhibits isolated dispersion curves which are identified as single particles and multi-particle bands. Our two-particle bound state analysis is restricted to a ladder approximation of the Bethe–Salpeter equation, and the existence of bound states depend on whether or not Gaussian domination for the four-point function is verified. It is known that two-particle bound states appear below the two-particle band if Gaussian domination does not hold. Here, we show that two two-particle bound states appear above the two-particle band if Gaussian domination is verified. We also show how the complete two-particle spectral pattern for these models can be understood by making a correspondence between the Bethe–Salpeter equation and a two-particle lattice Schrödinger Hamiltonian operator with attractive or repulsive spin-dependent delta potentials at the origin. A staggering transformation is used to relate the attractive and repulsive potential cases, as well as their associated Hamiltonians spectrum and eigenfunctions.

A numerical study of the problem of radiative heat transfer to magneto-hydrodynamic couette flow as affected by the conductance of the wall of the channel is performed in the paper. Numerical solutions are obtained for the temperature using the Runge–Kutta and the Newton–Raphson Shooting algorithm. Results obtained show that the rate of heat transfer increases with decreasing values of the Hartmann number when the wall is non-conducting, but increase with increasing values of the magnetic Reynolds number at a given value of electrical conductance.

Using the Nikiforov–Uvarov method, an application of the relativistic Duffin–Kemmer–Petiau equation in the presence of a deformed Hulthen potential is presented for spin zero particles. We derived first-order coupled differential radial equations which enable the energy eigenvalues as well as the full wavefunctions to be evaluated by using the Nikiforov–Uvarov method that can be written in terms of hypergeometric polynomials.

Molecular scattering differential cross sections have been measured for Ba(ClO₄)₂3H₂O, Ba(ClO₃)₂H₂O, BaCl₂2H₂O, Ba(NO₃)₂, BaCl₂ and BaO compounds at seven angles ranging from 60° to 120° at 10° intervals. Obtained values change in respect of effective atomic numbers for some Ba compounds at 60° and 120°. The obtained results have been compared with non-relativistic and relativistic theoretical values.

The ground state properties and the properties of the low-lying states of the beryllium isotopes are investigated using the extended version of the Antisymmetrized Molecular Dynamics Multi-Slater Determinant model. The theoretical method is found to be very useful to study the ground state properties of various nuclei including light unstable nuclei. Many experimental data can be successfully reproduced by the present approach. Binding energies, the energies of the 2₁⁺ states of the even-even isotopes, electromagnetic transition strengths and quadrupole moments of the proton and neutron distribution are calculated. The abnormal spin and parity of the ground state of ¹¹Be can be described with properly chosen interaction parameters. Interesting phenomena such as the development of cluster structures is observed.

Energy levels and radiative rates for transitions among 107 fine-structure levels belonging to the (1s²2s²2p⁶) 3s²3p⁶3d¹⁰, 3s²3p⁶3d⁹4l, 3s²3p⁵3d¹⁰4l, and 3s3p⁶3d¹⁰4l configurations of Ni-like Gd XXXVII have been calculated using the fully relativistic GRASP code. Radiative rates and oscillator strengths are tabulated for all allowed transitions among these levels. Additionally, collision strengths for transitions among the lowest 59 levels have been computed using the Dirac Atomic R-matrix Code. Resonances in the threshold region have been delineated, but results for collision strengths are tabulated only at energies above thresholds in the range 120 ≤ E ≤ 800 Ry. Effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, have also been calculated and are tabulated over a wide electron temperature range of 10^5.0 to 10^7.7 K. Our energy levels are assessed to be accurate to within 1%, while oscillator strengths, collision strengths, and effective collision strengths for all strong transitions are probably accurate to better than 20%.

We measured the spectrum of cesium emitted by a pulsed radio-frequency discharge in the region 1550 Å to 40 000 Å using concave grating spectrographs, Fabry–Perot interferometry, and Fourier transform spectroscopy. By varying the operating parameters of the discharge, we identified approximately 1700 of the more than 3000 spectral lines observed in this region as belonging to the spectrum of singly-ionized cesium (Cs II). Of these, 1683 were classified as transitions among 118 even and 165 odd energy levels. Partially or fully resolved hyperfine structure was analyzed for 579 lines.

The convective instability of a horizontal Hele–Shaw liquid layer subject to a time-varying gradient of temperature is investigated. The stationary component of the temperature gradient is considered either different or equal to zero. A dimensional analysis and an asymptotic study lead to two flow regimes depending on the order of magnitude of the Prandtl number Pr = O(1) or Pr >> 1 and Pr = O(ε²). The aspect ratio of the cell, ε, is considered smaller than unity. This analysis closely follows a previous work by Aniss et al [Phys. Fluids12 262 (2000)] in which a periodic gravitational modulation was considered in terms of the two flow regimes. The aim of the present paper is to examine the effects of temperature oscillations on the onset of convective instability for these two asymptotic cases. We have shown that for the first regime, modulation of temperature has no effect on the convective threshold. In contrast, the second regime presents a competition between the harmonic and subharmonic modes at the onset of convection.

A plane parallel laser beam, incident on a cylindrical dielectric fiber perpendicular to the axis of the fiber, focuses to small dimension as it approaches the axis. The focusing effect is enhanced by nonlinear self-focusing in the dielectric. For a given radius of the fiber one requires a specific laser intensity for which the beam focuses on the axis. In the axial region, however, the high intensity of the laser leads to tunnel ionization and optical breakdown of the dielectric, causing electron–hole pair production and plasma formation in the form of capillary. The plasma tends to self-defocus the laser.

Linear and nonlinear properties of ultra low-frequency (in comparison with the dust gyrofrequency), short wavelength (in comparison with the ion gyroradius) coupled dust-acoustic (DA) and dust-drift (DD) waves in a nonuniform dusty magnetoplasma with opposite polarity dust grains are investigated. By using the Boltzmann distribution for electrons and ions, and the hydrodynamic equations for the dust fluid, a set of nonlinear equations is derived. In the linear limit, a dispersion relation is obtained which exhibits coupling between the DA and DD waves. In the nonlinear regime, the nonlinear equations in a stationary frame can be reduced to an inhomogeneous differential equation. The latter yields both a dipolar vortex and a vortex street, depending on the translational speed of the vortices. The results should be useful for understanding the salient features of electrostatic waves and coherent nonlinear structures in Saturn's rings.

We characterized the trehalose- and sucrose-aqueous mixtures by means of neutron scattering experiment on IN13 at the ILL facility (Grenoble, France) that provide information on the motions of the sample hydrogens in a space–time window of ∼ 1 Å and 0.1 ns. Elastic scans are an efficient method to determine the temperature window in which relaxational processes appear in the system. In the transition range 250 K ≤ T ≤ 270 K, a strong and continuous loss of elastic intensity signals the presence of relaxational processes.

The evolution of effective diffusion coefficients D_eff of 13 different impurities in molten tellurium versus temperature T was studied. A new hyperbolic expression D_eff = f(T) for these impurities was established for effective segregation coefficients K_eff << 1 and for temperatures within the range 730 K–925 K. Experimental values of K_eff determined by zone melting process were used to calculate a series of 4 effective diffusion coefficients D_eff, at four different temperatures, for each impurity. These experimental results of D_eff were fitted with the new expression of D_eff = f(T) to confirm its validity. The diffusion mechanism of 13 impurities at the solid–liquid interface was then investigated under our previous experimental conditions (velocity v of interface, the starting concentration C₀, and number n of passes). These investigations confirmed that the temperature increase of tellurium molten zone was not convenient to reach an optimal purification by zone melting process.

Man's curiosity and fascination with diamonds date back to ancient times. The knowledge of the many properties of diamond is recorded during Biblical times. Antoine Lavoisier determined the composition of diamond by burning in O₂ to form CO₂. With the then existing awareness of graphite as carbon, the race began to convert graphite to diamond. The selective chemical synthesis of diamond has been pursued by Cagniard, Hannay, Moisson and Parson. On the basis of the thermodynamically predicted equilibrium line of diamond and graphite, P W Bridgman attempted extraordinary conditions of high temperature (>2200°C) and pressure (>100,000 atm) for the allotropic conversion of graphite to diamond. H T Hall was the first to successfully form bulk diamond by realizing the kinetic restrictions to Bridgman's (thermodynamic) high pressure high temperature direct allotropic conversion. Moreover, Hall identified catalysts for the faster kinetics of diamond formation. H M Strong determined the import of the liquid catalyst during Hall's catalytic synthesis. W G Eversole discovered the slow metastable low pressure diamond formation by pyrolytic chemical vapor deposition with the molecular hydrogen etching of the rapidly forming stable graphitic carbon. J C Angus determined the import of atomic hydrogen for faster etching for faster diamond growth at low pressure. S Matsumoto has developed plasma and hot filament technology for faster hydrogen and carbon radical generations at low pressure for faster diamond formation. However the metastable low pressure chemical vapor depositions by plasma and hot filament are prone to polycrystalline films. From Bridgman to Hall to Eversole, Angus and Matsumoto, much knowledge has developed of the importance of pressure, temperature, transition metal catalyst, liquid state of metal (metal radicals atoms) and the carbon radical intermediates for diamond synthesis. Here we advance this understanding of diamond formation by demonstrating the external magnetic organization of carbon, metal and hydrogen radicals for lower temperature and pressure synthesis. Here we show that strong static external magnetic field (>15 T) enhances the formation of single crystal diamond at lower pressure and even atmospheric pressure with implications for much better, faster high quality diamond formation by magnetization of current high pressure and temperature technology.

In this paper nonlinear-dispersive dissipative RLC transmission line is considered and envelope modulation is reduced to the modified cubic-quintic complex Ginzburg–Landau equation (CGLE) with derivatives in cubic terms. This obtained CGLE contains two free (from the line parameters) parameters, the nonlinear cubic gain and the linear gain. Modulational instability for the modified cubic-quintic CGLE is analyzed to lead to the generalized Lange and Newell criterion. We reformulate the derived CGLE as a third order ordinary system in standard form with the first derivatives on the left hand side in order to study the coherent structures.

The VIth International Workshop on Application of Lasers in Atomic Nuclei Research was held at Adam Mickiewicz University, Poznań in Poland from May 24 to 27, 2004. Its title this year was "Laser methods in the study of nuclei, atoms and molecules". Some topics are reviewed from a viewpoint of the atomic physics contribution to nuclear physics and its applications. It is suggested how this meeting should be organized in the future by taking the new geopolitics into account.

We consider the magneto-electric optical properties of the quantum vacuum and show that all the different phenomenona are related by Lorentz invariance. As a model calculation we show how crossed fields properties can be calculated starting from single field properties by using Lorentz transformations. Using this method we have studied for the first time the case of a crossed static magnetic field and electric field applied with one of these two fields parallel to the direction of light propagation. We also show that parallel field properties can be found using general symmetry properties.

The very large annihilation rates observed at room temperature in positron collisions with certain molecules have instigated the development of several models of positron annihilation based on the role of virtual processes, Feshbach resonances and bound states. One of the outcomes of these models has been the interest they have generated in investigations of the energy dependence of the annihilation cross-section in the vicinity of inelastic thresholds. The aim of this article is to provide a review of these recent studies and to highlight outstanding questions.

In this issue we commemorate Jean Brossel, one of the leaders of atomic physics in the post World-War II period, who passed away recently. Following his mentor, Alfred Kastler, as director of the Laboratoire de Spectroscopie Hertzienne at the Ecole Normale Supérieure in Paris, he developed it to become one of today's most prominent centres of atomic physics. In recognition, the laboratory has been renamed Laboratoire Kastler–Brossel (LKB). We find it important to recognize his life's activities in this journal's pages. Bernard Cagnac details the development of the physics at LKB during Brossel's time. For archival purposes, his life's activities and publications are included. A brief overview by one of us (HHS) of the origins of the double-resonance method (optical transitions coupled with rf resonances), and the part played by Francis Bitter, is presented.

The contributions of Jean Brossel to atomic physics, in particular to radiofrequency spectroscopy coupled with optical transitions, are presented. His part in the origins of the method, and in its ramifications over a half century in the Ecole Normale Supérieure in Paris, are described. A list of publications and the curriculum vitae of Brossel are appended.

The motivation of Francis Bitter to combine optical excitation and radiofrequencies for a spectroscopy with sensitivity adequate for work with radioactive atoms, and the implementation with Jean Brossel, are highlighted. The recounting provides background for the USA period of Brossel's early work to accompany the article by Bernard Cagnac on the life and contributions of Brossel.