Ibrahima Faye

Generalized oscillator strengths for dipole and octupole 3p → (3d, 4d, 5d), quadrupole and hexadecapole 3p → 4f transitions of argon atomic in the length and velocity formulations

The generalized oscillator strengths (GOS) of the argon transitions 3p6−3p5(3d, 4d, 5d) and 3p6−3p54f respectively for multiple strengths and are determined using the wavefunctions which have been generated from the CIV3 code of Hibbert. Calculations of these generalized oscillator strengths, as a function of momentum transfer, are also carried out respectively in the configuration interaction method and in the random phase approximation with exchange. The length and velocity forms have been used in this work. The gap between the absolute values of the generalized oscillator strength obtained in the theoretical calculations and those of the experimental results of Zhu et al have been noticeably reduced in the present work for the octupole excitations to 3p5(3d, 4d). This is due to the configuration interaction wavefunctions. The profiles and the positions of the extrema in the generalized oscillator strength have also received particular attention in the evaluation. The results of length and velocity form studies also show that the electron correlation effects are very significant for the excitations to 3p5(3d, 4d) but are found to have no great influence in the positions of the extrema.

Length and velocity form calculations of generalized oscillator strengths of dipole, quadrupole and monopole excitations of argon

The quadrupole, monopole and dipole generalized oscillator strengths (GOSs) as a function of momentum transfer are respectively calculated for these 3p6 → 3p5 (4p, 5p, 6p) and 3p6 → 3p5 (4s, 5s, 6s) transitions. Configuration interaction (CI) and random phase approximation with exchange (RPAE) methods are used in the determination of these GOS, in the length and velocity forms. The code of Hibbert has been used to generate the wavefunctions from which a partial of argon GOSs are been computed. The present work has reduced the gap between the absolute values of the theoretical calculations of GOSs and those of the experimental results of Zhu et al for the quadrupole excitations to 3p5 (4p, 5p). The profile of our quadrupole GOS 3p6 → 3p55p transition agrees well with the experimental result of Zhu. The best agreement (0.7%) is observed between the (length) first maximum position and the experimental one for the quadrupole GOS 3p6 → 3p54p transition. The present velocity GOS minimum position for the dipole excitation in 3p6 → 3p54s and the calculated velocity GOS maximum position of the monopole 3p6 → 3p54p transition are in good agreement with the experimental observations (differences of 1.82% and 3.08%, respectively). Correlation effects decrease with increasing of the excited state principal quantum number and have no great influence on the extrema positions.

Electron impact excitation of helium in Debye plasma

The probability, differential, and integral scattering cross sections of the 11S→21S and 11S→21P transitions of helium have been calculated in the first Born approximation. The projectile-target interactions depending on the temperature and the density of plasma are described by the Debye-Huckel model. Wave functions of the target before and after collision were modeled by non orthogonal Hartree-Fock orbitals. The wave functions parameters are calculated with the Ritz variational method. We improve our unscreened first Born approximation integral cross sections by using the BE-scaled (B stands for binding energy and E excitation energy) method. The second Born approximation has also been used to calculate the excitation cross sections in Debye plasma. Our calculations are compared to other theoretical and experimental results where applicable.

Stark broadening parameters calculation of the allowed 4471 Å line and forbidden 4470 Å component of neutral helium with different electric microfield distribution functions

The influence of an electric microfield distribution function (EMDF) on line shapes and on Stark broadening parameters is studied. For this purpose, we use different EMDFs obtained by theoretical calculations and computer simulation methods to calculate the allowed 4471?? neutral helium line and its forbidden 4470?? component. Correlation effects are shown by considering different categories of plasmas, weakly coupled plasmas and strongly coupled plasmas, with large gaps of temperature and density.

Coupling the Navier-Stokes Equations with a Short Term Dynamic of Sand Dunes

Our paper deals about sand transport problem near the seabed. We consider model for short-term dynamics of dune (STDD) and megariple morphodynamics built in (Faye et al., Discrete and Continuous Dynamical Systems, 29; No3 March 2011, 1001–1030), that we coupled with a Navier-Stokes equations. We study the evolution of the dunes and an existence and uniqueness results are established for coupled short-term model. In this framework we derive an asymptotic expansion with respect to the small parameter 𝜖 of its solution, and characterize the terms of the expansion.