Light scattering by a finite obstacle and fano resonances

The conditions for observing Fano resonances at elastic light scattering by a single finite-size obstacle are discussed. General arguments are illustrated by consideration of the scattering by a small (relative to the incident light wavelength) spherical obstacle based upon the exact Mie solution of the diffraction problem. The most attention is paid to recently discovered anomalous scattering. An exactly solvable one-dimentional discrete model with nonlocal coupling for simulating diffraction in wave scattering in systems with reduced spatial dimensionality is also introduced and analyzed. Deep connections between the resonances in the continuous and discrete systems are revealed.     

Light scattering by a finite cylinder containing a spherical cavity using Sh-matrices

We use the Sh-matrix formalism that contains the shape-dependent parameters of the T-matrix to derive an analytical solution for the light scattering from a finite cylinder containing a spherical cavity. The integral expressions for the Sh-matrix elements are simpler than those of the T-matrix elements and the case of a sphere embedded in a finite cylinder these integrals can be solved analytically.     

Light scattering by erythrocytes under conditions of osmotic imbalance in a cell-surrounding medium system

A model for changes in the sizes of erythrocytes under conditions of osmotic imbalance in a hypoosmotic medium is proposed assuming free diffusion of water through the erythrocyte membrane. Equations relating the minimum and maximum osmotic resistances to the shape of an erythrocyte in an isotonic medium are obtained. A numerical simulation is used to determine how the optical attenuation coefficient varies as a result of the swelling and hemolysis of erythrocytes; this provides a foundation for a new optical method for determining the osmotic resistance of erythrocytes. This method does not require exerting a force on the erythrocytes, is distinguished by simplicity and high speed, and can be implemented using standard spectrophotometers.     

Parametrization of the scattering indicatrix for a finite scattering medium

We consider a method of parametrizing the radiative scattering indicatrix. The scattering indicatrix is represented as projections , , on the axes of a Cartesian system of coordinates. Examples are discussed of the experimental determination of these parameters for a model dispersive medium consisting of a solution of polystyrene latex particles in water.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 36–39, October, 1985.     

Light scattering in a fluid far from equilibrium

The integrated intensity is computed of each of the two Brillouin lines of a stationary fluid far from equilibrium in the presence of a temperature gradient. The difference in intensity found is due to mode-coupling effects and deviates appreciably from an extrapolation of earlier calculations near equilibrium.     

Light scattering by a 2D electron system with spin-orbit interaction in a strong magnetic field

We theoretically investigate light scattering by electrons of a 2D system in a strong magnetic field perpendicular to the plane of the system (the filling factor is smaller than two, i.e., only the states of the zeroth Landau level are filled). Analysis is carried out in the resonance approximation, in which the frequencies of the incident and scattered light are close to the effective separation between the conduction band and one of the branches of the valence band of the semiconductor. Spin splitting of the Landau level in the conduction band associated with Zeeman and the spin-orbit interactions is taken into account. The dynamic screening effects are considered in the random phase approximation (RPA).     

Two-dimensional radiative transfer in a finite scattering planar medium

The source function, radiative flux, and intensity at the boundaries are calculated for a two-dimensional, scattering, finite medium subjected to collimated radiation. The scattering phase function is composed of a spike in the forward direction super-imposed on an isotropic background. Exact radiative transfer theory is used to formulate the problem and Ambarzumian's method is used to obtain results. Using the principle of superposition, the results for any step variation in incident radiation are expressed in terms of universal functions for the semi-infinite step case. Two-dimensional effects are most pronounced at large optical thicknesses and albedos.     

Light scattering from colloids

This paper presents a review of light scattering results on static and dynamic properties of ordered colloidal suspensions of charged polystyrene particles and fractal colloidal aggregates. Our studies on static structure factor,S(Q), of ordered monodisperse colloidal suspensions and binary mixtures of particles with different particle diameters, measured by angle-resolved Rayleigh scattering will be discussed. This will include determination of bulk modulus using gravitational compression and observation of colloidal glass (inferred from splitting of the second peak inS(Q)). Dynamic light scattering, with real time analysis of scattered intensity fluctuations, is used to get information about Brownian dynamics of the particles. Recent advances in the field of light scattering from colloidal aggregates which show fractal geometry will also be discussed.     

Light scattering properties of a rough-ended optical fibre

Uniform wide-angle irradiation of a laser beam is achieved by roughening chemically the output end of an optical fibre. The angular distribution of the scattered light is analysed experimentally as a function of the incident angle of the laser beam into the input end of the fibre and the length of the rough core surface at its output end.     

Light scattering as a form of modulation spectroscopy

In the conventional modulation spectroscopy the optical constants of a solid are modulated by means of an external parameter (stress, electric field, etc). As a result of the presence of elemental excitations in the solid (usually phonons) a spontaneous modulation of the optical constants takes place at the frequency of the excitations. This modulation can be observed in light scattering experiments (Raman and Brillouin). Such measurements yield information about the frequency and density of states of the excitations (conventional Raman and Brillouin measurements), about their interaction with electronic states, and about the electronic transitions themselves (resonant scattering experiments). The theory of resonant Raman and Brillouin scattering in semiconductors will be discussed in connection with that of other modulation experiments (piezoreflectance, stress induced birefringence). Another closely related phenomenon, that of spatial-dispersion-induced birefringence will also be presented.     

Light scattering lineshape in opaque materials

The wavevector distribution excited by light scattering in opaque materials is calculated and compared to recently observed asymmetrical Brillouin lineshapes.     

周期性加隔板有限长圆柱壳声散射

研究内部真空周期性加隔板圆柱壳在水中的声散射特性.壳体振动用薄壳理论的Donnell方程描述,隔板振动用相互独立的薄板纯弯曲振动和平面应力状态下的振动方程描述.考虑轴向、切向、径向三个方向的力和弯矩共同作用导出了散射声场的解析表达式.数值计算给出远场收发合置情况下的角度-频率谱图,并据此进行机理分析.通过与内部周期性加环肋圆柱壳声散射的角度-频率谱图比较发现,除周期加肋产生的Bragg散射波与弯曲Bloch-Floquet波外,加隔板的情况还存在明显的隔板共振亮线,并且发生隔板共振与壳体弹性波、Bragg散射波、弯曲Bloch-Floquet波耦合的现象.通过实验对理论进行了验证,在实验的频率范围内,Bragg散射亮线与理论符合得很好,部分Bloch-Floquet波散射亮线和隔板共振散射亮线也与理论符合.     

Light scattering evidence of a central component in ice Ih

High resolution Raman spectra of ice I_h single crystal in the frequency range 0–30 cm^?1 are reported, at various temperatures. For the first time evidence is given for the existence of a Lorentzian central component in all scattering configurations. A polarization analysis of the spectra clearly shows that the central mode cannot be ascribed to the high frequency tails of the Brillouin doublet, nor to the disorder induced phonon background even accounting for renormalization of the phonon propagator. The epectral features indicate the existence of a direct coupling between the light and some relaxation mechanism of the crystal.A model is suggested to account for the excess scattering and for the activation of the acoustic phonon density of states.     

Multi-crossing dynamics of a multi-particle Landau-Zener (LZ) system: Dynamics matrix approach

This paper investigates multi-crossing dynamics of multi-particle Landau-Zener (LZ) systems applying Dynamic matrix approach (DMA) that is found to generalize probability amplitudes. It is also observed that for exceedingly low frequencies, the system exhibits one crossing while for high frequencies, the multi-crossing. It is shown that for particular phenomenological parameters of the system, there is total population transfer that achieves the values one or zero useful for implementing quantum logic gates.     

Light scattering in cholesteric liquid crystals with a large pitch

Optical properties of cholesteric liquid crystals with a pitch larger than the wavelength of light are considered. Normal waves of the medium and the Green function of the electromagnetic field are analyzed. A general algorithm based on the application of the Kirchhoff method is proposed for calculating the scattered light intensity in media with a one-dimensional periodic structure. The WKB vector method is used for calculating the spatial correlation function of thermal fluctuations of the director. It is found that the transformation of two fluctuation modes takes place is some regions. The angular and polarization dependences of the intensity of light scattered from fluctuations of the director are calculated. It is found, in particular, that the intensity of scattering is a nonmonotonic function of the size of the system.     

Light scattering from a fluid with a stationary temperature gradient

The spectrum of light, scattered from a fluid with a stationary temperature gradient, is calculated on the basis of fluctuating hydrodynamics. Explicit expressions are obtained for the spectrum of the scattered light which is no longer symmetric around the frequency of the incident light. In particular the difference in height and intensity of the Brillouin lines is given. Furthermore the shift in the position of the maximum of the Rayleigh line is calculated.     

Light scattering from a fluid with a stationary temperature gradient

The spectrum of light scattered from a system in which a stationary temperature gradient is maintained is calculated on the basis of fluctuating hydrodynamics. Explicit expressions are obtained for the frequency dependence of the intensity of the modified Brillouin lines.     

Critical-point symmetry in a finite system

At a critical point of a second-order phase transition the intrinsic energy surface is flat and there is no stable minimum value of the deformation. However, for a finite system, we show that there is an effective deformation which can describe the dynamics at the critical point. This effective deformation is determined by minimizing the energy surface after projection onto the appropriate symmetries. We derive analytic expressions for energies and quadrupole rates which provide good estimates for these observables at the critical point.