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Scattering Process (scattering + process)
Selected AbstractsSimulation of general linear dielectric properties in TLMINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5-6 2002John Paul Abstract The simulation of linear dispersive dielectric materials in time-domain TLM requires the inclusion of frequency-dependent material properties in the scattering process. For media having frequency dependencies described by a single pole or a pair of complex poles, for example Debye, Drude or Lorentz, it is straightforward to develop individual algorithms on a case-by-case basis. However, this approach lacks generality and when applied to the modelling of media displaying more complicated frequency dependencies, somewhat lengthy calculations need to be evaluated each time a new material is required. To address this difficulty, this paper describes methods for obtaining the iteration algorithm for general linear isotropic dielectric media. The results obtained using different ,,-transform methods are compared and an example of a frequency-dependent structure is simulated. Copyright © 2002 John Wiley & Sons, Ltd. [source] Dipole moments of polyenic oligomeric systems.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2005Part II, allenes, molecular organic wire resistivities: polyacetylenes, polyynes Abstract Polyacetylenic, allenic and polyynic molecular wire series, containing electron-donor (D) and electron-acceptor (A) groups as two terminal units of the oligomeric bridge (D,wire,A), can be well described by means of a one-dimensional conduction model, which considers a scattering process of electrons through the charge-transfer conduction bridge. The conduction constants (,i) of the oligomeric structures of the three molecular series under study were determined from the functional dependence between the dipole moment of the oligomers (,n) and the ,-molecular orbital bridge length (L). According to our one-dimensional molecular organic wire model: where ,o is the dipolar moment of the first compound of the oligomeric series without a bridge unit (n,=,0) and ,, is a limit value for L,,,,. By means of the Landauer theoretical expression for the conductance of a metallic one-dimensional conductor and our molecular wire conduction constants (,i), we determined the intrinsic resistivities associated with the molecular resistances of these oligomeric wires. Using this approach we determined, for the first time, the linear and non-linear contributions to the net molecular resistivity. The order of magnitudes of the linear resistivities determined in these oligomeric systems agrees very well with the expected results of experimental measurements for macroscopic wires. Copyright © 2005 John Wiley & Sons, Ltd. [source] Nonresonant scattering of relativistic electron by relativistic muon in the pulsed light fieldLASER PHYSICS LETTERS, Issue 3 2009E.A. Padusenko Abstract The nonresonant scattering of an electron by a muon in the pulsed light field in the frame of the Born approximation in general relativistic case is investigated theoretically. The approximation when a pulsewidth is considerably greater than the characteristic time of the wave oscillation is considered. The analytical expressions for the amplitude and cross-section of electron-muon nonresonant scattering process are derived in case of moderately strong elliptically polarized pulsed laser wave. It is demonstrated, that the process partial cross-section in the pulsed laser field differs essentially from the corresponding one in the field of plane monochromatic wave. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Stimulated Raman scattering in Nd:SrWO4LASER PHYSICS LETTERS, Issue 1 2005H. Jelínková Abstract Stimulated Raman scattering process in Nd:SrWO4 crystal was employed to frequency down-shift the fundamental frequency of a Nd:YAG mode-locked laser system. A single-pass configuration of Raman crystal was investigated for this purpose. After that Nd:SrWO4 laser was built and coherent pumping by alexandrite laser radiation was used. The simultaneous generation of stimulated Raman scattering was proofed for the case of Q-switching and mode-locking of Nd:SrWO4 Raman cavity. For Nd:YAG 50 ps long (1064 nm) pulsed pumping a single-pass first Stokes maximum energy and conversion efficiency were 1.6 mJ and 25% , respectively. With the free-running Nd:SrWO4 laser the maximum energy of 90 mJ at wavelength 1057 nm was obtained. Q-switching with the LiF:F,2 saturable absorber gave up to 1.3 mJ energy at the first Stokes frequency (1170 nm) in the pulse length of 3 ns. In mode-locking regime (with saturable absorber ML51 in dichlorethan or 3955 in ethanol), the total generated energy was 1.8 mJ and 2.4 mJ for ML51 and 3955 dyes, respectively. The SRS output at 1170 nm was approximately 20% of those values. (© 2005 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Effective mass of InN estimated by Raman scatteringPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Jung Gon Kim Abstract We have estimated the longitudinal effective mass (m,) of electron in n-type InN films by Raman scattering. The samples were grown by MOVPE (metal organic vapor phase epitaxy) with free carrier concentration of n =6.7×1018 -9.9×1018 cm -3 according to Hall measurement. A weak Raman signal observed at ,430 cm -1 at room temperature was sharpened and shifted to higher frequency toward the A1(TO)-phonon mode at 447 cm -1 with increasing n. This mode was assigned to the lower branch (L - ) of the longitudinal-optic-phonon-plasmon-coupled (LOPC) mode. The line shape was carefully analyzed by a semi-classical line-shape fitting analysis assuming deformation potential and electro-optic coupling mechanisms for the light scattering process. A line-shape fitting analysis was conducted by adjusting three major parameters; electron density, effective mass and plasmon damping rate. The analysis well reproduced values of electron density and mobility deduced by Hall measurement. Electron effective mass of m,*/m0 = 0.05 (±0.01) was also obtained as the best-fit parameter. The result agrees well with previous data obtained by other optical methods. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Conversion of an electron,hole plasma into a high density excitonic state in ZnO epitaxial thin filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004Y. Toshine Abstract Time-resolved luminescence spectra of an exciton-exciton scattering process and an electron,hole plasma (EHP) were measured in ZnO epitaxial thin films by the optical Kerr gate method. At moderate excitation density below critical Mott density, stimulated emission of luminescence due to the exciton,exciton scattering process (P band) was observed. The P band shows a red shift and spectral narrowing in the first 1,2 ps after the excitation which reflects a thermal redistribution of excitons in the n = 1 excitonic state. On the other hand, at high excitation density above the critical Mott density, stimulated emission of the luminescence due to the EHP was observed. After thermalization of the EHP, the luminescence intensity of the EHP band decreases with time, and the EHP band converts to the P band after ,10 ps through a reverse Mott transition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 3D Monte Carlo simulation including full Coulomb interaction under high electron concentration regimesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008Tadayoshi Uechi Abstract We construct 3D Monte Carlo (MC) simulations including the full Coulomb interaction as accurately as possible. In order to achieve this goal, the usual strategy for the MC approach is employed; the Coulomb potential is split into the long-range and the short-range parts. The long-range part of the Coulomb potential is taken into account by solving the Poisson equation, in which the simulation parameters such as mesh size, charged-particle size, time step etc are carefully optimized by performing the particle simulations with turning off artificially all short-ranged scatterings. The short-range part of the Coulomb potential is incorporated into the MC simulations as scattering processes by developing a new scattering model, in which the impurities are localized in real space. It is shown that the present 3D MC simulations successfully explain the entire regime of the electron mobility as a function of impurity concentrations. In addition, it is found for the first time that the plasma frequency is modulated due to localization of the background impurities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The role of phonons in establishing a non-equilibrium quasiparticle state in small gap multiple tunnelling superconducting tunnel junctionsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004A. G. Kozorezov Abstract We derive expressions for phonon escape times from a thin superconducting film. The escape time is determined by the rate of scattering conversion for phonons propagating beyond the critical cone for total internal reflection. The conversion is due to different scattering processes for the groups of Cooper pair breaking and sub-gap phonons. For pair breaking phonons the most efficient conversion mechanism is through the interaction with the condensate. For sub-gap phonons the conversion rate is much slower and for plane parallel films is due to elastic scattering at surface or interface roughness resulting in significantly slower escape times. We discuss implications of slow escape time for sub-gap phonons for the properties of the recently observed new non-equilibrium state in small gap multiple tunnelling superconducting tunnel junctions. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Entanglement-buildup through charged-exciton decay in a semiconductor quantum dotPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2004Ulrich Hohenester Abstract We analyze the decay of a single-electron charged exciton in a quantum dot embedded in a field effect structure. We show how the quantum properties of the charged exciton are transferred through tunneling and relaxation to the spin entanglement between electrons in the dot and contact, carefully examine the proper theoretical description of the underlying scattering processes, and identify the pertinent disentanglement mechanisms. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||