Omar M. Aldossary

Quantum Hall physics with cold atoms in cylindrical optical lattices

We propose and study various realizations of a Hofstadter-Hubbard model on a cylinder geometry with fermionic cold atoms in optical lattices. The cylindrical optical lattice is created by copropagating Laguerre-Gauss beams, i.e.~light beams carrying orbital angular momentum. By strong focusing of the light beams we create a real space optical lattice in the form of rings, which are offset in energy. A second set of Laguerre-Gauss beams then induces a Raman-hopping between these rings, imprinting phases corresponding to a synthetic magnetic field (artificial gauge field). In addition, by rotating the lattice potential, we achieve a slowly varying flux through the hole of the cylinder, which allows us to probe the Hall response of the system as a realization of Laughlins thought experiment. We study how in the presence of interactions fractional quantum Hall physics could be observed in this setup.

Electron angular distributions of noble gases in sequential two-photon double ionization

We present an angle resolved study of photoelectrons emitted from ions of the noble gases neon, argon and krypton by means of time-of-flight spectroscopy. The ionic targets are generated in a sequential two-photon process induced by the free-electron laser FLASH. Values of the anisotropy parameters and are derived from electron angular distribution measurements in the photon energy range from 38 to 91 eV and compared with recent theoretical calculations.

Theoretical study of LiK and LiK+ in adiabatic representation

The potential energy curves have been calculated for the electronic states of the molecule LiK within the range 3 to 300 a.u., of the internuclear distance R. Using an ab initio method, through a semiempirical spin-orbit pseudo-potential for the Li (1s2) and K (1s22s22p63s23p6) cores and core valence correlation correction added to the electrostatic Hamiltonian with Gaussian basis sets for both atoms. The core valence effects including core-polarization and core-valence correlation are taken into account by using an l-dependent core-polarization potential. The molecular orbitals have been derived from self-consistent field (SCF) calculation. The spectroscopic constants, dipole moments and vibrational levels of the lowest electronic states of the LiK molecule dissociating into K (4s, 4p, 5s, 3d, and 5p) + Li (2s, 2p, 3s, and 3p) in 1, 3Σ, 1, 3Π, and 1, 3Δ symmetries. Adiabatic results are also reported for 2Σ, 2Π, and 2Δ electronic states of the molecular ion LiK+ dissociating into Li (2s, 2p, 3s, and 3p) + K+ and Li+ + K (4s, 4p, 5s, 3d, and 5p). The comparison of the present results with those available in the literature shows a very good agreement in spectroscopic constants of some lowest states of the LiK and LiK+ molecules, especially with the available theoretical works. The existence of numerous avoided crossing between electronic states of 2Σ and 2Π symmetries is related to the charge transfer process between the two ionic systems Li+K and LiK+.

Topological Soliton Solutions of .2 C 1/-dimensional KdV Equation with Power Law Nonlinearity and Time-dependent Coefficients

1 Radiation Physics Laboratory, Department of Physics, Faculty of Sciences, Badji Mokhtar University, Anaba, Algeria 2 Faculty of Electronic Engineering, Department of Telecommunications, University of Nis, Nis, Serbia 3 Department of Mathematics, Qaid-i-Azam University, Islamabad, Pakistan 4 Department of Physics, King Saud University, Riyadh, Saudi Arabia 5 Department of Mathematical Sciences, Delaware State University, Dover, USA

Guiding of atoms in helical optical potential structures

The classical dynamics of a cold atom trapped inside a static helical optical potential is investigated based on the Lagrangian formalism, which takes into account both the optical light field and the gravitational field. The resulting equations of motion are solved numerically and analytically. The topology of the helical optical potential, which drives the trapped cold atom, is responsible for two different types of oscillations, namely: the local oscillations, whereby the atomic motion is confined in a region smaller than the light field wavelength and the global oscillations, when the atomic motion is extended to larger regions comparable to the beam Rayleigh range Local oscillations guide the atom along the helical structure of the optical potential. The global oscillations, which constitute the main topic of our paper, define the atomic motion along the z-axis as an oscillation between two turning points. For typical values of the beam waist the turning points are symmetrical around the origin. For large values of the beam waist the global oscillations become asymmetric because the optical dipole potential weakens and the gravitational potential contributes to the determination of the turning points. For sufficiently large values of the beam waist there are no global oscillations and only one upper turning point defines the atoms global motion.

Heat Transfer in a Couple Stress Fluid over a Continuous Moving Surface with Internal Heat Generation and Convective Boundary Conditions

This investigation reports the boundary layer flow and heat transfer characteristics in a couple stress fluid flow over a continuos moving surface with a parallel free stream. The effects of heat generation in the presence of convective boundary conditions are also investigated. Series solutions for the velocity and temperature distributions are obtained by the homotopy analysis method (HAM). Convergence of obtained series solutions are analyzed. The results are obtained and discussed through graphs for physical parameters of interest.

OSCILLATORY FLOW OF FOURTH-ORDER FLUID IN A POROUS HALF SPACE

This work describes the incompressible flow of fourth-order fluid in a porous half space. The flow in the porous space is caused by the porous plate oscillations in its own plane. Modified Darcys law has been taken into account to discuss the flow characteristics in a porous space. Numerical solution of the governing nonlinear problem is obtained and the effects of various pertinent parameters are discussed.

An investigation of the size-dependent cohesive energy and the structural stability of spherical metallic nanoparticles

The size-dependent potential parameters method is used to investigate the effect of many-body interactions on the structural stabilities and the cohesive energy of molybdenum (Mo) and tungsten (W) spherical metallic nanoparticles. The total interaction energy is represented in terms of a two-body Mie-type potential plus a three-body Axilord?Teller-type potential. Results emphasized the importance of multi-body forces to explain nano-structures. The predicted cohesive energy for these nanoparticles is observed to decrease with decreasing sizes, a result which is in agreement with experimental results.

Radiation pattern of two identical emitters driven by a Laguerre-Gaussian beam: An atom nanoantenna

We study the directional properties of a radiation field emitted by a geometrically small system composed of two identical two-level emitters located at short distances and driven by an optical vortex beam, a Laguerre-Gaussian beam which possesses a structured phase and amplitude. We find that the system may operate as a nanoantenna for controlled and tunable directional emission. Polar diagrams of the radiation intensity are presented showing that a constant phase or amplitude difference at the positions of the emitters plays an essential role in the directivity of the emission. We find that the radiation patterns may differ dramatically for different phase and amplitude differences at the positions of the emitters. As a result the system may operate as a two- or one-sided nanoantenna. In particular, a two-sided highly focused directional emission can be achieved when the emitters experience the same amplitude and a constant phase difference of the driving field. We find a general directional property of the emitted field that when the phase differences at the positions of the emitters equal an even multiple of \pi/4, the system behaves as a two-sided antenna. When the phase difference equals an odd multiple of \pi/4, the system behaves as an one-sided antenna. The case when the emitters experience the same phase but different amplitudes of the driving field is also considered and it is found that the effect of different amplitudes is to cause the system to behave as a uni-directional antenna radiating along the interatomic axis.

Appearance of Plasmons in Fullerenes

The valence electrons of fullerenes may be regarded as spherical distributions with a finite width of a jellium-like potential giving rise to collective motions of this orange peel electron cloud. They cause strong enhancement of the photoionization cross section, a resonant behavior phenomenon know as plasmon excitations. The number and characteristic features of these excitations will be discussed.