Preparation and Characterization of ZnO Nanocrystalline Layers

This work consists on the study of the optical properties of zinc oxide layers. These Layers are elaborated under various conditions by cathode sputtering on glass substrates and by thermal oxidations of Zn layers deposited on different types of substrates by vacuum evaporation. The oxidation treatments of Zn are made in oxygen atmosphere at temperatures between 400°C and 450&degC for different times. The analyses by diffraction of X-rays, Optical Microscopy and Scanning electron microscopy enabled us to understand that the zinc oxide films deposited by cathode sputtering on a glass substrate and having a thickness of at least 240 nm and those prepared by thermal oxidation at 450&degC during 2 hours of layers of Zn on an alumina substrate are homogeneous and consist of grains of size 30 nm. The optical transmission measurements show that the gap is around 3.02 eV for layers obtained by oxidation and 3.3 eV for those deposited by sputtering. These samples have a good optical transparency in the visible.

Theoretical investigation of the pressure broadening D1 and D2 lines of cesium atoms colliding with ground-state helium atoms

Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential energy curves of the low-lying CsHe molecular states, as well as the related transition dipole moments, are carefully computed from ab initio methods based on state-averaged complete active space self-consistent field-multireference configuration interaction(SACASSCF-MRCI) calculations, involving the spin-orbit effect, and taking into account the Davidson and BSSE corrections.The absorption and emission reduced coefficients are determined in the temperature and wavelength ranges of 323-3000 K and 800-1000 nm, respectively. Both profiles of the absorption and the emission are dominated by the free-free transitions,and exhibit a satellite peak in the blue wing near the wavelength 825 nm, attributed to B^2Σ1/2^+→ X^2Σ1/2^+/transitions. The results are in good agreement with previous experimental and theoretical works.

Bound in continuum states and induced transparency in mesoscopic demultiplexer with two outputs

We investigate the electronic transport in a simple mesoscopic cross structure made of two wires(stubs)grafted at the same point along a quantum waveguide.We show that the structure may exhibit important phenomena such as bound in continuum(BIC)states.These states are transformed into electromagnetically induced transparency(EIT)resonance by detuning slightly the lengths of the stubs.The last phenomenon is used to propose and study a mesoscopic demultiplexer device with an input waveguide and two output waveguides.We give closed-form expressions of the geometrical parameters that allow a selective transfer of a given state in the first waveguide without perturbing the second waveguide.The effect of temperature on the transmission resonances is also examined by using Landauer-Büttiker formula.The analytical results of the dispersion relation and transmission and reflection coefficient are obtained using the Green's function method.

Li(2p←2s)+Na(3s)pressure broadening in the far-wing and line-core profiles

This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures.The results show the existence of three satellites,in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm.For the line-core region,by adopting the simplified Baranger model,the line-width and line-shift rates are determined,and their variation law with temperature is examined.No published data were found to compare these results with.

Directional H^(2) Compression Algorithm: Optimisations and Application to a Discontinuous Galerkin BEM for the Helmholtz Equation

This study aimed to specialise a directional H^(2)(DH^(2))compression to matrices arising from the discontinuous Galerkin(DG)discretisation of the hypersingular equation in acoustics.The significantfinding is an algorithm that takes a DG stiffness matrix andfinds a near-optimal DH^(2) approximation for low and high-frequency problems.We introduced the necessary special optimisations to make this algorithm more efficient in the case of a DG stiffness matrix.Moreover,an automatic parameter tuning strategy makes it easy to use and versatile.Numerical comparisons with a classical Boundary Element Method(BEM)show that a DG scheme combined with a DH^(2) gives better computational efficiency than a classical BEM in the case of high-order finite elements and hp heterogeneous meshes.The results indicate that DG is suitable for an auto-adaptive context in integral equations.