Stokes parameters of an electromagnetic light wave on scattering

Stokes parameters of an electromagnetic light wave on scattering have been discussed, which permit us to study the spectral degree of polarization of the far-zone scattered field. An example of scattering of a spatially coherent electromagnetic light wave from a quasi-homogeneous medium has been discussed to illustrate the changes of the Stokes parameters and the changes of the spectral degree of polarization of the far-zone scattered field.     

Spectral shifts produced by scattering of Rectangular Gaussian Schell Model sources from a deterministic medium

Within the accuracy of the first-order Born approximation, we investigate the scattering of Rectangular Gaussian Schell Model (RGSM) sources incident upon a deterministic medium. The analytical expression for the far-zone scattered spectrum is derived. Numerical results show that red shift or blue shift can be produced in the far-zone scattered spectrum, and the spectral shifts are mainly influenced by the scattering direction and the source parameters (i.e., the source width and the source correlation widths along the x and y directions).     

Condition for far-zone spectral isotropy of an electromagnetic light wave on weak scattering

The far-zone spectral isotropy of an electromagnetic light wave on scattering has been discussed. It is shown that a sufficient condition for the far-zone spectral isotropy of an electromagnetic light wave on scattering can be expressed by the following two requirements: the two-point correlation function of the dielectric susceptibility of the scattering medium obeys the so-called scaling law, and the normalized spectrum of the incident light wave has the same distribution along the two perpendicular directions.     

Scattering of light in an inhomogeneous fluctuating plasma

Scattering of light in an inhomogeneous fluctuating plasma is treated whose mean density distribution is given by a solution of the Korteweg-de Vries equation. The amplitude and phase correlation functions are computed for given mean density and spectral function of the density fluctuations.The non-linear effect of the mean inhomogeneous density distribution on the scattered light leads to beatings in the spectral functions of the amplitude and phase correlations. It is shown that the covariance function for the log-amplitude (which is to first order proportional to the intensity of the scattered light) can be approximated in a large L-region by a power law whose exponent is smaller than in the homogeneous case.     

Three-dimensional generalization of the Van Cittert-Zernike theorem to wave and particle scattering

Coherence properties of primary partially coherent radiations (light, X-rays and particles) elastically scattered from a 3D object consisting of a collection of electrons and nuclei are analyzed in the Fresnel diffraction region and in the far field. The behaviour of the cross-spectral density of the scattered radiation transverse and along to the local direction of propagation is shown to be described by respectively the 3D Fourier and Fresnel transform of the generalized radiance function of a scattering secondary source associated with the object. A relativistic correct expression is derived for the mutual coherence function of radiation which takes account of the dispersive propagation of particle beams in vacuum. An effect of the spatial coherence of radiation on the temporal one is found; in the Fresnel diffraction region, in distinction to the field, both the longitudinal spatial coherence and the spectral width of radiation affect the longitudinal coherence. A solution of the 3D inverse scattering problem for partially coherent radiation is presented. It is shown that squared modulus of the scattering potential and its 2D projections can be reconstructed from measurements of the modulus and phase of the degree of transverse spatial coherence of the scattered radiation. The results provide a theoretical basis for new methods of image formation and structure analysis in X-ray, electron, ion, and neutron optics.     

Photon Doppler Velocimetry and Simulation of Ejection of Particles from the Surface of Shock-Loaded Samples

The results of photon Doppler velocimetry of ejecta from shock-loaded metal samples are reported. The experiments have been performed with tin and lead samples of a given thickness and a given surface roughness. The direct numerical simulation of the process of mass ejection from the surface of shock-loaded samples is performed for conditions close to experimental by the smoothed particle hydrodynamics method. The areal density and initial velocity distribution of the volume density of ejecta are determined. Using these results, we calculate the time dependence of the profile of the volume density at the expansion of the formed dust cloud to air. Applying an approach based on the transport equation for the correlation function of the scattered field, the main parameters of the velocity distribution of ejecta, areal density of ejecta, etc. are reconstructed from spectral photon Doppler velocimetry data. The experimentally observed temporal dynamics of spectra, which is caused by the drag of dust in air, is described at an appropriately chosen size dispersion of dust particles. The masses of ejecta reconstructed from experimental data are in agreement with the smoothed particle hydrodynamics results.     

Scattering of scalar light wave from a Gaussianben Schell model medium

The scattering of scalar light wave from a random medium with a correlation function of Gaussian–Schell model distribution is studied. It is shown that the properties of the scattered field, i.e., the spectral density and the spectral degree of coherence of the scattered field, are closely related to the properties of the scattering medium, including the scaled effective radius and the scaled correlation length of the correlation function.     

Superfluorescent rayleigh scattering from suspensions of dielectric particles

We demonstrate that superfluorescent scattering of light can occur when laser light is incident on a collection of dielectric Rayleigh particles suspended in a viscous medium. Using a linear stability analysis, an expression for the spatiotemporal evolution of the scattered (probe) field is derived. An approximate condition for the progression of the interaction into the nonlinear regime is deduced and it is shown that, in the nonlinear regime, the scattered field intensity shows the characteristic quadratic dependence on particle density expected from a superfluorescent or superradiant process, once the effects of pump depletion are accounted for.     

A direct method of particle sizing based on the statistical processing of scattered photons from particles executing Brownian motion

A direct method of determining the mean diameter of particles executing Brownian motion is presented. The temporal coherence of the scattered field from submicroscopic particles illuminated by laser light is a function of both the integration time and the particle diameter. The temporal degree of coherence of the time-averaged scattered intensity decreases as the integration time increases. Statistical processing of the scattered photons leads to a method of particle sizing (average diameter), which circumvents the need for digital autocor-relation or power spectral estimation.     

Method for Describing the Angular Distribution of Optical Radiation Scattered by a Monolayer of Ordered Spherical Particles (Normal Illumination)

We have developed a method for describing the angular distribution of intensity of radiation scattered by a monolayer of homogeneous spatially ordered monodisperse spherical particles normally illuminated by a plane circularly polarized electromagnetic wave. The method is based on the quasicrystalline approximation (QCA) of the theory of multiple scattering of waves (TMSW) using the multipole expansion of fields and the tensor Green function in vectorial spherical wavefunctions. The method is applied for analyzing the characteristics of radiation scattered by a partially ordered monolayer and a monolayer with a nonideal lattice. The results of calculations are compared with the available experimental data on the position of the first-order diffraction peak on the angular and spectral dependences of the intensity of radiation scattered by a closely packed monolayer with a nonideal triangular lattice of SiO₂ particles. Good conformity of the results has been established.     

多层球对高斯波束散射的德拜级数研究

基于广义洛伦兹-米氏理论,利用多层球粒子散射系数的德拜级数展开公式,提出了一种新的研究多层球粒子对高斯波束散射的方法。计算结果与已有的广义洛伦兹-米氏理论算法的计算结果吻合得很好。利用该方法有效分离了折射率分布满足指数变化规律的多层球粒子对高斯波束散射的远区散射场中多阶彩虹的干涉强度分布。数值模拟了双层球的归一化双一阶彩虹强度分布以及各层的一阶彩虹艾里结构。最后分析讨论了高斯波束的入射位置和束腰半径对多层球单阶彩虹强度分布的影响。     

Vibrational sum frequency scattering from a submicron suspension

A novel application of vibrational sum frequency generation (VSFG) is developed to study the molecular properties of the surface of submicron particles in suspension. The Rayleigh-Gans-Debye scattering theory is extended to extract the local molecular response from the macroscopic nonlinearly scattered spectral intensity. These results demonstrate the use of VSFG to investigate quantitatively the surface molecular properties of submicron particles, dispersed in solution. It provides information on the order and density of alkane chains and allows us to determine the elements of the local second-order surface susceptibility.     

Scattering and Transmission by a Monolayer of Spheres: A Study on the Monolayer Structure

The angular distribution of scattered light and the transmission of radiation through a monolayer of monodisperse spherical particles at variable particle concentration are studied. The scattering of light by a single particle is calculated with the classical Lorentz‐Mie theory. For a monolayer of mono‐dispersed spherical particles, if the monolayer density is less than 0.5 and the particle size parameter is larger than 5, effects from multiple scattering and dependent scattering can be excluded so that only steric interactions are considered. It is found that the scattering pattern, especially in the forward and backward directions, and the transmission are strongly dependent on the monolayer density.     

Pair-structure matrix of random collection of particles: Implications for light scattering

Scattering of light fields from random collections of particles of different types is considered. A new matrix called pair-structure matrix characterizing the correlations between particles of the same and of different types is introduced. This matrix reduces to the pair-structure factor of scattering collection [Opt. Lett. 34, 1762 (2009)] in the case when the particles in the collection are all of the same type. For illustration of the importance of the new matrix the formula for the degree of coherence of a polychromatic plane wave scattered from a collection of particles of different types is derived.     

基于自回归模型的超细颗粒动态光散射模拟

为了获取超细颗粒动态散射光模拟信号, 在分析超细颗粒动态散射光信号特性的基础上, 通过建立动态光散射随机过程的自回归(AR)模型, 利用Levison-Durbin递推算法确定模型参数, 并给出了单峰、双峰分布颗粒信号模拟的模型阶数确定方法, 从而提出了一种基于AR模型的态光散射信号模拟方法。分别对50 nm, 300 nm, 1000 nm, 50 nm与1000 nm, 100 nm与500 nm, 300 nm与1000 nm的单峰、双峰分布颗粒在模型阶数分别为1, 1, 1, 57, 28, 40时进行了模拟, 得到的模拟信号的光强自相关函数与理论值吻合, 用累积法对单峰分布颗粒反演和双指数法对双峰分布颗粒反演, 相对误差分别小于0.58%和3.7%, 因此, 单峰分布颗粒信号模拟需一阶模型, 双峰分布颗粒信号模拟粒径不同所需阶数不同。     

Propagation of cosmic rays in the foam-like Universe

The model of a classical spacetime foam is considered, which consists of static wormholes embedded in Minkowski spacetime. We examine the propagation of particles in such a medium and demonstrate that a single thin ray undergoes a specific damping in the density of particles depending on the traversed path and the distribution of wormholes. The missing particles are scattered around the ray. Wormholes was shown to form DM halos around point-like sources and, therefore, the correlation predicted between the damping and the amount of DM may be used to verify the topological nature of dark matter.     

Time interval photoelectron statistics of non-gaussian scattered light

Time interval distributions are evaluated for coherent light scattered by a small collection of independent, but polydispensive, particles. Two situations are considered: when the number of scatterers within the scattering volume, N, is fixed, and when N is allowed to fluctuate randomly with a Poisson distribution.     

On the Spectral Distribution of Equilibrium Radiation and Zero-Point Fluctuations in the Coulomb System

The consideration of equilibrium radiation in plasma-like media shows that the spectral energy distribution of such radiation differs from that of Planck equilibrium radiation. Based on the previously derived relation for the spectral energy density of equilibrium radiation in the system of charged particles, accounting for finite damping in a medium with spatial dispersion, the limiting case of infinitesimal damping dispersion is considered. It was shown that zero-point vacuum fluctuations being a component of the total spectral energy distribution in the medium should be renormalized when using certain models for the transverse plasma permittivity. In this case, renormalized zero-point vacuum fluctuations become dependent on plasma parameters. The possibility of the manifestation of this effect is discussed.     

On the use of the multifrequency method for studying scattered fields during the antenna measurements in an anechoic chamber

We consider a method of far-zone wideband antenna measurements performed at discrete frequencies with subsequent synthesis of the tested-antenna response in the time domain for separating the useful signal and interference due to scattering. Experimental results of a study of the scattered fields arising during the measurements of characteristics of centimeter-wave horn antennas on a standard facility in an anechoic chamber are presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 47, No. 12, pp. 1066–1077, December, 2004.     

Sizing of Irregular Particles Using a Phase Doppler System

Response of a phase Doppler system to irregularly shaped particles is examined and shown to deviate qualitatively as well as quantitatively from the spherical particles. Nevertheless, the measured phase distributions based on an ensemble of particles exhibit a high degree of order and simplicity. The experimental data and the stochastic modeling of the process have shown that the phase Doppler technique can be used successfully for in-situ sizing and velocimetry of irregular particles. In the case of irregular crystalline particles, mean size and standard deviation can be deduced without requiring any assumptions regarding the functional form of the size distribution. As opposed to other optical techniques, phase Doppler can be used, in principle, near the backscattering location, so that a single optical window would be employed for transmission of laser light and collection of the scattered signals. Furthermore, size measurements can be velocity-resolved, i.e. a size distribution can be associated with each bin of the velocity histogram.