Field of a Point Source Within Perfectly Conducting Parallel-Plates in a Homogeneous Biisotropic Medium

The spherical wave scattering response by a perfectly conducting open–ended waveguide in a biisotropic medium is obtained. Interestingly, the vector diffraction problem is reduced to the scattering of a single scalar field, this scalar field being the normal component of either a left–handed or a right–handed Beltrami field. Here, we explicitly consider the scattering of the left–handed field component, that of the other scalar field being analogously tractable. The solution is constructed with the aid of the Wiener–Hopf technique.     

Relaxation time for a charge carrier due to its scattering from other charge carriers in superlattices

A calculation of relaxation time for (i) electron–electron scattering in a modulation-doped superlattice of type-I and (ii) electron–electron, hole–hole and electron–hole scattering processes in a compositional superlattice of type-II has been performed, using Fermi's golden rule. As compared to a two-dimensional electron gas system, both intralayer and interlayer interactions, between charge carriers in a superlattice, contribute to relaxation time. It is found that scattering processes at all possible value of momentum transfer contribute to relaxation time, for a given value of temperature and carrier density. We further find interlayer interactions in a superlattice make a significant contribution to relaxation time. Relaxation time is found to decrease on increasing temperature, carrier density and single particle energy, in a superlattice. The computed relaxation time for an electron (hole) in a superlattice enhances on increasing the width of layer consisting of electrons (holes). The electron–hole (hole–electron) scattering process in a type-II superlattice yields maximum contribution to the relaxation time when a hole layer lies exactly in between two consecutive electron layers.     

Characterization of Submillimeter Wave Absorbers from 200–600 GHz

This paper presents measurements of both specular and non-specular scattering from several submillimeter wave absorber materials designed for antenna testing and from low-cost carpet materials. The frequency range is 200–600 GHz in specular scattering, and 300–400 GHz in non-specular scattering measurements. The constructed bistatic test bench allows testing of the full continuous angular range of 0°–90°. The measurement results show large differences in performance of different materials. It is shown that reflectivities below –50 dB over limited angular ranges are possible with a correct alignment of the material. Also, low-cost carpet materials have lower than –15 dB reflectivities in most angles, and may be useful in non-critical parts of the antenna test range. The results can be used to optimise the absorber placement inside an antenna range, concerning both best performance and lowest cost.     

Resonant elastic scattering of light from single quantum wells in semiconductor multilayers

A theory is developed for steady-state elastic scattering of light via quasi-2D excitons from a quantum well (QW) whose interfaces are randomly rough. The study is mainly focused on the angle dependences of radiation giving direct information about static disorder responsible for the elastic scattering. A nonlocal excitonic susceptibility is expressed in terms of random profile functions of QW interfaces. Treated is elastic scattering of light from a disordered QW in the following actual dielectric environments: (i) a uniform background, (ii) a Fabry–Perot film with rough boundaries, and (iii) a semiconductor microcavity. The cross-sections are derived analytically for scattering of linearly polarized light to the lowest (Born's) approximation with arbitrary roughness statistics. The spectral and angle dependencies of scattering intensity are analyzed numerically in the absolute-value scale with Gaussian correlation of interface roughness. The probability 10⁻² was found for the exciton-mediated scattering of a photon from a QW interface roughness whose root-mean-square height is on the level of 2×10⁻¹ nm. This probability is shown to exceed by two orders of magnitude that is typical of resonant scattering from either a single semiconductor surface or rough boundaries of a semiconductor Fabry–Perot film containing the QW. The scattering spectrum of a QW placed in a microcavity is predicted to have a doublet structure whose components are associated with the cavity exciton–polaritons.     

Relativistic calculations of inelastic collisions between electrons and atoms

The Feynman S-matrix formalism is used to consider the inelastic collisions of electrons with a hydrogen atom. The two leading Feynman diagrams are calculated, and the 1s-2s transition is treated in detail. Results are given for scattering amplitudes at energies of 1.0–8.0 (atomic units) and for various scattering angles, as well as the differential cross sections for direct scattering in the energy region 1.36–118.5 keV. On the basis of comparison with nonrelativistic calculations, we conclude that relativistic effects are appreciable and increase with energy. Total cross sections are calculated in both nonrelativistic and relativistic approximations. The difference between them increases with energy and is 15–20% for energies of 20–50 keV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 7–12, August, 1977.     

Scattering mechanism in doped semiconductors with a smooth random field

The scattering mechanism of charge carriers in doped compensated semiconductors with a smooth random field is considered in the interval of temperatures 4–100°K and of impurity concentrations 10¹⁴–10¹⁸ cm^–3. It is shown that in the conditions mentioned above at the lowest temperatures scattering in the Coulomb field associated with charged impurity dominates, while at elevated temperatures scattering in the smooth random field is important. Scattering by phonons and by resonant and virtual levels associated with the random potential is insignificant in the present conditions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 23–27, February, 1984.     

Double line stimulated Raman scattering in benzene

Simultaneous stimulated Raman scattering at the 992 cm^–1 and the 3063 cm^–1 line of benzene is observed by mode-locked ruby laser pulse excitation. The double line stimulated Raman scattering is initiated by self-focusing. The influence of small-scale self-focusing, self-phase modulation, and cross-phase modulation on the double line stimulated Raman scattering is discussed. At low pump pulse intensities, before the onset of small-scale self-focusing, the steady-state Raman gain factors of both Raman lines are determined by Raman energy conversion efficiency measurements.     

Effect of localized spins in coherent transport through quantum dots

The effect of localized spins on the quantum coherence in solids is discussed. A quantum dot with an odd number of electrons can be a model system for a localized spin. It is experimentally shown that a spin flip scattering by a quantum dot pulls the trigger of quantum decoherence. On the other hand, spin flip scattering is the basic process to construct the Kondo singlet state around a magnetic impurity. Through an interference effect of the Kondo state (the Fano–Kondo effect) in a side-coupled dot system, we show experimentally that the Kondo singlet state is quantum mechanically coherent. The analysis of the Fano–Kondo lineshape indicates the locking of the phase shift to π/2, which is in agreement with theoretical predictions. The Fano–Kondo effect is also observed in an Aharonov–Bohm ring, in which a quantum dot is embedded, and also indicates the phase shift locking to π/2.     

Origin of dark holographic scattering patterns in photorefractive crystals

We explain the origin of recently reported dark parametric holographic scattering patterns observed in photorefractive strontium–barium niobate (SBN) and barium–calcium titanate (BCT) crystals. Taking into account the model for parametric four-wave-mixing processes in photorefractive crystals, exponential gain factors are presented for the scattering patterns and compared with the gain for the scattering background. We interpret the dark scattering patterns as a result of counteracting energy-transfer processes. PACS 42.65.Hw; 42.70.Nq     

Influence of the quantum dot shape on the determination of the electronic structure and electron decoherence

Theoretical calculations of electron–phonon scattering rates in AlGaN/GaN quantum dots (QDs) have been performed by means of effective mass approximation in the frame of finite element method. The influence of a symmetry breaking of the carrier's wave function on the electron dephasing time is investigated for various QDs shapes. In a QD system the electron energy increases when the QD shape changes from a spherical to a non-spherical form. In addition, the influence of the QD shape upon the electronic structure can be modulated by external magnetic fields. We also show that the electron–acoustic phonon scattering rates strongly depend upon both the QD shape and the applied magnetic field. As an additional parameter, the QD shape can be used to modify the electron–acoustic phonon interaction in a wide range. Moreover, the scattering rate of different transitions, such as Δm=0(1), presents distinct magnetic field dependency.     

Nonperturbative, Unitary Quantum-Particle Scattering Amplitudes from Three-Particle Equations

We here use our nonperturbative, cluster decomposable relativistic scattering formalism to calculate photon–spinor scattering, including the related particle–antiparticle annihilation amplitude. We start from a three-body system in which the unitary pair interactions contain the kinematic possibility of single quantum exchange and the symmetry properties needed to identify and substitute antiparticles for particles. We extract from it a unitary two-particle amplitude for quantum–particle scattering. We verify that we have done this correctly by showing that our calculated photon–spinor amplitude reduces in the weak coupling limit to the usual lowest order, manifestly covariant (QED) result with the correct normalization. That we are able to successfully do this directly demonstrates that renormalizability need not be a fundamental requirement for all physically viable models.     

The modified Beckmann–Kirchhoff scattering theory for surface characteristics in-process measurement

This paper focuses on how the scattering theory can be applied to the analysis of the surface characteristics in an in-process optical measurement. The mean scattered intensity distributions from a surface without and with the additional layers are presented based on the modified Beckmann–Kirchhoff scattering theory. The results show that the introduction of the additional layers only affects rough surfaces. The light scattered from a rough surface under the additional layers seems to be scattered from a bare rough surface with a different surface parameter in the small angle approximation. The experiment is conducted with pixel gray value measurement along the main direction of light scattering stripe to verify the theoretical analysis. The experimental curves can well fit the proposed model, which testifies the correction of the modified Beckmann–Kirchhoff scattering theory.     

Effect of elastic scattering on the kinetics of mesic atom formation

The differential, total and transport elastic cross sections are calculated with an adiabatic effective (µ^––H) potential and with regard to inelastic transitions. The elastic cross section is greater than the inelastic one by an order of value in the atomic-capture energy region. The excess increases with particle mass. The effect of the elastic scattering on the energy distribution of Coulomb capture is considered within the approximation of continuous elastic energy losses. An appreciable increase of the capture probability due to elastic scattering is obtained in the low-energy region.     

Magnetoresistance of the compound CeRu2Ge2

In this work we present a magnetoresistance study on the CeRu₂Ge₂ compound. We analyze the ρ(T) curves for several applied magnetic fields using the electron–magnon scattering model for a ferromagnetic spin arrangement. From this analysis, the field dependence of the energy gap of the magnon spectrum is obtained. The magnetoresistance ρ(H) at various temperatures arises from a normal metal contribution with an additional scattering mechanism due to electron–magnon interaction.     

Electron ionization rate in III–V ternary semiconductors

Theoretical calculations are presented for the ionization rate of electrons in III–V ternary semiconductor compounds considering alloy scattering and carrier-carrier interaction, in addition to optical phonon scattering and ionization scattering. However, alloy scattering is found to be a weak interaction. Fairly good agreement is obtained for Ga_1–x In _x As withx=0.14 and 0.53 with the experimental results and for Ga_0.5 Al_0.5 As with the existing theoretical result which used an indirect method. The alloy scattering potential has been taken in the form of energy band-gap difference. The calculations can be used for any ternary semi-conductor.     

Theory of electronic light scattering in lateral superlattices with Rashba spin–orbit coupling under quantizing electric and magnetic fields

The influence of an in-plane electric and out-of-plane magnetic field on the electronic light scattering is calculated for a lateral semiconductor superlattice within Rashba spin–orbit interaction. Sharp resonances are predicted to appear when the Raman shift matches one frequency of the Wannier–Stark ladder. The spin–orbit interaction gives rise to a dispersion of the exact one-particle eigenstates and an associated finite width of the Raman line, which can be tuned by the electric and magnetic field. When the Bloch frequency is located in this Raman line, a Fano resonance is observed.     

Orientational self-pumped phase conjugation of a light beam in a layer of a nematic liquid crystal with nonreciprocal feedback

Self-pumped phase conjugation of a Nd: YAG laser beam by forward stimulated orientational scattering in a nematic liquid crystal layer with a nonreciprocal feedback loop is investigated. It is found that the threshold of phase-conjugate wave generation is the lowest when the phase shift difference of pumping and scattering waves in the loop is /2.Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 3–4, pp. 304–311, March–April, 1995.     

Rayleigh and Mandelstam-Brillouin light scattering in chalcogenide glasses of the As-S system

The Rayleigh light scattering in chalcogenide glasslike alloys of the As-S system is investigated. The velocities of longitudinal hypersound, elasto-optical constants, extinction coefficients, and scattering losses have been determined. It is shown that an increase in the amount of sulfur in alloys leads to an increase in chemical differentiation and, as a result, to an increase in the intensity of Rayleigh scattering and in inherent optical losses.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, 823–826, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Asymptotic description of solitary wave trains in fully nonlinear shallow-water theory

We derive an asymptotic formula for the amplitude distribution in a fully nonlinear shallow-water solitary wave train which is formed as the long-time outcome of the initial-value problem for the Su–Gardner (or one-dimensional Green–Naghdi) system. Our analysis is based on the properties of the characteristics of the associated Whitham modulation system which describes an intermediate “undular bore” stage of the evolution. The resulting formula represents a “non-integrable” analogue of the well-known semi-classical distribution for the Korteweg–de Vries equation, which is usually obtained through the inverse scattering transform. Our analytical results are shown to agree with the results of direct numerical simulations of the Su–Gardner system. Our analysis can be generalised to other weakly dispersive, fully nonlinear systems which are not necessarily completely integrable.