共查询到20条相似文献,搜索用时 78 毫秒
1.
Small-angle scattering (SAS) is a powerful experimental technique in condensed matter physics for studying structural features
of inhomogeneities of colloidal dimensions. So far the technique has been largely exploited to study thin samples for which
the single scattering approximation, for the radiation-matrix interaction, holds good. The single scattering approximation
is invalid when the thickness of the sample exceeds the scattering mean free path. This situation calls for a guideline to
analyse the scattering data having significant contribution from multiple scattering. Since multiple scattering broadens the
scattering profile, the beam broadening nature of multiple scattering can also be exploited, by making the sample suitably
thick, to study large size inhomogeneities which are otherwise inaccessible to a small-angle scattering set up because of
its resolution constraints. The present article presents a review and extension of the theoretical basis for analysing multiple
scattering data from the point of view of a recent formalism on multiple small-angle scattering. The formalism is valid for
both monodisperse and polydisperse scattering media characterized by the presence of large size inhomogeneities in the matrix.
It is shown that multiple scattering from a polydisperse sample can be described by a system of coupled integrodifferential
equation. However, multiple scattering from a monodisperse sample can be described by a Fokker-Planck type of equation. These
equations have been analysed with an emphasis laid on the nature of the structural information pertaining to the inhomogeneities
which is extractable from the multiple scattering profile. When the linear dimension of inhomogeneities becomes comparable
to the scattering mean free path of the radiation in the sample, the statistical nature of the medium becomes pronounced.
The statistical nature of the medium modulates the scattering profile. The modulation effect could be broadening or narrowing
of the profile depending upon the nature of the inhomogeneities and their population distribution. The limiting regimes of
validity and the implications of various approximations, frequently used to analyse the scattering data, have been indicated. 相似文献
2.
Inspired by the problem of elastic wave scattering on wrinkled interfaces, we studied the scattering of ballistic electrons on a wrinkled potential energy region. The electron transmission coefficient depends on both wrinkle amplitude and periodicity, having different behaviors for positive and negative scattering potential energies. For scattering on potential barriers, minibands appear in the electron transmission, as in superlattices, whereas for scattering on periodic potential wells the transmission coefficient has a more complex form. Besides suggesting that tuning of electron transmission is possible by modifying the scattering potential via voltages on wrinkled gate electrodes, our results emphasize the analogies between ballistic electrons and elastic waves even in scattering problems on non-typical configurations. 相似文献
3.
B. P. Sharfarets 《Acoustical Physics》2005,51(5):578-586
A method is developed for solving problems of multiple scattering by an aggregate of bodies in a homogeneous unbounded medium. For this purpose, the problem on the multiple scattering produced by two bodies in the field of a plane wave is first considered under the assumption that the initial unperturbed scattering amplitudes of both scatterers are known. The solution is constructed by considering plane waves multiply rescattered by the scatterers. Integral equations are obtained that allow one to calculate the resulting scattering amplitude of each scatterer and the combined scattering amplitude of the system of two scatterers. It is shown that knowledge of the solution to this problem is sufficient to solve the problem on the scattering field of a system consisting of an arbitrary number of scatterers. Expressions for the scattering amplitude in the case of an arbitrary primary field are presented. The relationship between the integral equations describing the multiple scattering in a homogeneous space and the multiple scattering by a single scatterer located near an interface is demonstrated. Approximate expressions are given for calculating the scattering amplitude in the case of multiple scattering. 相似文献
4.
为实现利用光学方式对微纳尺度粒子性质的研究,探讨了亚微米线及亚微米球对光电磁波的散射效应.微纳米尺度粒子的光学散射,散射粒子尺寸与入射光波长尺寸可满足米氏(Mie)散射条件.利用Matlab数值模拟的方式,将分析结果以模拟图的形式清晰地展现出来.满足尺寸条件的层状粒子以及任意多个散射粒子存在时对电磁波的散射都可采用Mie散射分析方法,并且针对多粒子散射,分析了散射体位于不同位置时对散射造成的影响.通过分析光学散射光场相关的微分散射截面及近场散射电磁场分布,可得出散射光场随散射角度的变化趋势,以及散射光场受各类因素的影响,包括入射光偏振态、散射粒子尺寸、散射粒子结构及粒子构成层数、散射粒子数量等的影响,也包括一些隐含因素对散射光场的影响,如散射粒子与周围介质的相对折射率.本文的科学意义体现在:与入射光波长尺寸可比的亚微米尺度的粒子,可用作传感器,对于其位移的探测可通过光学方式来实现,而由于粒子本身特性对散射光的影响具有一定的参考价值,从而使通过光学方式对机械位移的读出具有更高准确度.研究结果对于光学方式探测亚微米线机械振动具有指导意义. 相似文献
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The radiation transfer equation for a semi -infinite scattering medium is solved. The solution provides information on the size distribution function of the scattering particles, starting from experimental data on the multiple scattering of electromagnetic radiation. A solution is obtained for the case where the probability of scattering is given by the solution of Mie's problem. 相似文献
7.
D.K. Ferry 《Surface science》1978,75(1):86-91
The scattering rate and momentum relaxation time for scattering of electrons in the quasi-two-dimensional quantized levels of an inversion or accumulation layer on a semiconductor surface is calculated for interactions via the polar-optical phonon. This interaction represents an important scattering mechanism in compound semiconcudctors. The quantization of the motion perpendicular to the surface enhances the scattering by this process over the bulk scattering. 相似文献
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《中国物理快报》2017,(9)
The existence of the sea surface is bound to affect the electromagnetic(EM) scattering from marine targets. When dealing with the composite scattering from targets over a sea surface by applying high-frequency EM theories,the total scattering field can be decomposed into three parts in low sea states, namely, the direct scattering from the sea surface, the direct scattering from targets and the coupling scattering between the sea surface and targets. With regard to high sea states, breaking waves make the direct scattering from the sea surface and the coupling scattering more complicated. To solve this issue, a scattering model is proposed to analyze the composite scattering from a ship over a rough sea surface under high sea states. To consider the effect of breaking waves,a three dimensional geometric model is adopted together with Ufimtsev's theory of edge waves for the scattering from a breaker. In addition, the coupling scattering between targets and breaking waves is taken into account by considering all possible scattering paths. The simulated results indicate that the influence of breaking waves on the scattering field from the sea surface and on the coupling field is non-negligible, and the numerical results also show the effectiveness of the proposed scattering model. 相似文献
10.
V. K. Lukyanov E. V. Zemlyanaya K. V. Lukyanov E. I. Zhabitskaya M. V. Zhabitsky 《Physics of Atomic Nuclei》2014,77(1):100-109
Differential cross sections for elastic pion scattering on a number of nuclei at energies between 130 and 290 MeV are calculated. For this purpose, use is made of a microscopic optical pion-nucleus potential that was obtained on the basis of the Glauber theory of high-energy scattering and which is determined by the density distribution of pointlike target nucleons and by the pion-nucleon scattering amplitude. The calculation of the cross sections in question is based on solving the respective relativistic wave equation. Three parameters of the pion-nucleon amplitude are fitted in performing a comparison with experimental data. These are the total cross section for pion-nucleon scattering, the ratio of the real to the imaginary part of the forward pion-nucleon scattering amplitude, and the slope parameter. The resulting values of these parameters are then compared with their counterparts for scattering on free nucleons. The character of nuclear-matter-induced changes in these parameters is studied. 相似文献
11.
Far-field weak scattering theory is applied to the case of high-frequency broad-bandwidth acoustic scattering from a thermally generated buoyant plume in a controlled laboratory environment. To first order, the dominant scattering mechanism is thermally driven sound-speed variations that are related to temperature deviations from ambient. As a result, the received complex acoustic scattering is a measure of the one-component three-dimensional Fourier transform of the temperature difference field measured at the Bragg wave number. The Bragg wave number vector is the difference between the scattered and incident wave vectors. Solving for its magnitude yields the Bragg scattering condition; this is the Fourier component of the plume variability that produces scattering. Results are presented for multistatic scattering from unstable and turbulent plumes using a parallel scattering geometry. The data justify application of the far-field weak scattering theory to the present case of a thermal plume. As a consequence, quantitative results on medium variability can be inferred using high-frequency broad-bandwidth acoustic scattering. Particular attention is given to the role of anisotropy of the variability of the scattering field in determining the validity of far-field Bragg scattering. 相似文献
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《Waves in Random and Complex Media》2013,23(2):269-295
This paper deals with a TE plane wave scattering from a thin film with one-dimensional disorder by means of the stochastic functional approach. The thin film is one-dimensionally inhomogeneous in the horizontal direction with infinite extent, and is homogeneous in the vertical direction with finite thickness. Based on an approximate wavefield representation in terms of a Wiener–Hermite expansion in a preceding paper (Tamura et al., 2004, Waves in Random Media, 14, 435–465), the first- and second-order incoherent scattering cross-sections are presented in explicit forms and scattering properties are discussed. The scattering properties vary entirely with the film thickness. In a case where the thickness is smaller than a few wavelengths in the thin film, enhanced scattering and associated enhanced scattering may appear as sharp peaks or dips on the second-order incoherent scattering distribution if the thin film has guided wave modes. When the thickness becomes sufficiently larger than the wavelength inside the film, a new enhanced scattering phenomenon appears as gentle peaks on the second-order incoherent scattering distribution in four special directions. Such four directions are the directions of forward scattering, specular reflection, backscattering, and the symmetrical direction of forward scattering with respect to the normal of the film surface.The first-order incoherent scattering occurs distinctly in four such directions. Such enhanced scattering is independent of the existence of the guided wave modes inside the thin film, and deeply relates to the structure of the thin film with one-dimensional disorder that has infinite correlation in the vertical direction. For SiC and glass thin films having one-dimensional disorder with a Gaussian correlation and three types of exponential correlation, the first- and second-order incoherent scattering cross-sections are illustrated in figures. The narrow enhanced scattering peaks appear for the glass film in a thin case. The gentle enhanced peaks turn up for both the SiC and glass films in a thick case. Furthermore, the optical theorem is calculated for several cases. It is then found that the error of the optical theorem decreases and the performance of the wavefield is improved by taking into account the second-order incoherent scattering. 相似文献
14.
基于辐射传播方程及多重散射基础理论,利用Fraunhofer近似,对颗粒媒质的多重散射光强进行了计算。研究了光学厚度对多重散射的影响,揭示了多重光散射的角分布特征,光强大小随光学厚度的变化,以及单散射引起的误差等方面的规律。为实际的颗粒媒质的光学测量等提供了理论根据。 相似文献
15.
This paper deals with a TE plane wave scattering from a thin film with one-dimensional disorder by means of the stochastic functional approach. The thin film is one-dimensionally inhomogeneous in the horizontal direction with infinite extent, and is homogeneous in the vertical direction with finite thickness. Based on an approximate wavefield representation in terms of a Wiener-Hermite expansion in a preceding paper (Tamura et al., 2004, Waves in Random Media, 14, 435-465), the first- and second-order incoherent scattering cross-sections are presented in explicit forms and scattering properties are discussed. The scattering properties vary entirely with the film thickness. In a case where the thickness is smaller than a few wavelengths in the thin film, enhanced scattering and associated enhanced scattering may appear as sharp peaks or dips on the second-order incoherent scattering distribution if the thin film has guided wave modes. When the thickness becomes sufficiently larger than the wavelength inside the film, a new enhanced scattering phenomenon appears as gentle peaks on the second-order incoherent scattering distribution in four special directions. Such four directions are the directions of forward scattering, specular reflection, backscattering, and the symmetrical direction of forward scattering with respect to the normal of the film surface.The first-order incoherent scattering occurs distinctly in four such directions. Such enhanced scattering is independent of the existence of the guided wave modes inside the thin film, and deeply relates to the structure of the thin film with one-dimensional disorder that has infinite correlation in the vertical direction. For SiC and glass thin films having one-dimensional disorder with a Gaussian correlation and three types of exponential correlation, the first- and second-order incoherent scattering cross-sections are illustrated in figures. The narrow enhanced scattering peaks appear for the glass film in a thin case. The gentle enhanced peaks turn up for both the SiC and glass films in a thick case. Furthermore, the optical theorem is calculated for several cases. It is then found that the error of the optical theorem decreases and the performance of the wavefield is improved by taking into account the second-order incoherent scattering. 相似文献
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A. I. Sokolovskaya 《Journal of Russian Laser Research》1998,19(3):244-305
Some results associated with the fundamental investigations of stimulated scattering of light in various media are reported. A number of problems of adaptive optics based on stimulated scattering is studied. Concrete results of experimental investigations of physically important characteristics of conventional (spontaneous) and stimulated Raman scattering are presented and discussed. Among them are the scattering indicatrix and the relations between the phases of laser radiation incident on a substance and stimulated scattering. These results were first obtained in the G. S. Landsberg Optical Department of the P. N. Lebedev Physical Institute of the Russian Academy of Sciences. Data on excitation sources and the radiation detection technique are systematized. The main characteristics of spontaneous Raman scattering and forward and backward stimulated Raman scattering (energy parameters, pulse duration, pulse shape, divergence, brightness, spectral width, far- and near-field intensity distributions) are presented. The results on dynamic holography, phase conjugation of light in stimulated scattering, and reconstruction and recording of information (images) with the help of amplifying dynamic holograms are presented. The physical mechanisms responsible for the interference field recording and the phase conjugation of pump radiation in stimulated light scattering are discussed. The data on phase conjugation for stimulated scattering excited by picosecond optical pulses and the results associated with the effect of excitation geometry on the optical phase conjugation in the case of stimulated scattering excited by nanosecond pulses are presented. 相似文献
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首先建立大尺度分层介质粗糙面散射的物理模型, 基于Stratton-Chu积分方程和Kirchhoff近似导出了粗糙面散射场的计算公式. 采用高斯随机粗糙面来模拟实际的分层介质粗糙面, 通过数值计算得到了正下视单站雷达接收到的后向散射回波. 理论推导了散射场强度与表面粗糙度之间的定量关系, 并从数值仿真的角度分析了表面和次表面的粗糙度对散射回波的影响, 给出了散射场随粗糙度变化的曲线. 最后考察了分层介质的电特性参数(介电常数和电导率)对分层粗糙面散射场的影响, 并对计算结果做出了分析. 相似文献