Scattering of Two Spinless Particles in 3D Formulation with Coulomb Admixtures

Scattering of two spinless charge particles for simple forces including coulomb admixtures is calculated without partial wave decomposition. The coulomb interaction being taken is of the type of screened coulomb potential. For the forces range is not infinite, the standard scattering theory is applied. The differential and total cross section are calculated and coulomb effects are shown.     

Light Scattering by Small Particles: an Ellipsoidal Model That Uses a Quasistatic Approach

Optics and Spectroscopy - To describe light scattering by small nonspherical particles, we have constructed an ellipsoidal model using a quasistatic approximation. The semiaxes of the model...     

Raman Scattering in Three-Dimensional Photonic Crystals

The optical properties of three-dimensional photonic crystals associated with the form of reflection spectra from their surface (appearance of a forbidden gap in the energy spectrum) and with the specific features of Raman scattering are analyzed. Idealized models of the energy band structure of photonic crystals are studied. Expressions for the group velocity of photons with energy close to the forbidden gap are derived. Experimental results on the Raman scattering in photonic crystals based on artificial opal as well as in fused silica are discussed. Bands due to quantum-size effects (presence of nanoclusters in fused silica and nanoglobules forming the lattice of globular photonic crystals) were manifested in the spectra of inelastic light scattering. It is proposed to use photonic crystals for the creation of sensitive sensors of organic and inorganic substances using modern Raman techniques.     

Optical Multiple Scattering by Particles

When an optical beam is incident on particles that are randomly distributed, and if the fractional volume is small, single scattering theory is adequate to explain the scattering characteristics of the medium. However, when the fractional volume is increased, multiple scattering effects cannot be ignored. This paper reviews the fundamental theories of multiple scattering including radiative transfer and diffusion theories. Also included are recent studies on polarization effects, localization, enhanced backscattering, resonant localization, pulse scattering and scattering in dense media.     

Reaction Mechanisms in a Multichannel Scattering Theory for Identical Particles

Exchange effects in rearrangement reactions are studied in the framework of a general algebraic theory of identical-particle scattering. An algebraic definition of reaction mechanisms proposed previously is used to distinguish the contributions to scattering amplitudes made by different exchange processes. Previous statements concerning the number of possible exchange mechanisms and their relative weight factors are rigorously proved. The results of this paper differ from those obtained in previous studies, as here identical clusters of particles are also treated as indistinguishable. Received March 31, 1994; revised Juli 22, 1994; accepted for publication September 29, 1994     

Stationary Scattering Theory for a Charged Particles Transport Problem

We consider a nonautonomous transport problem, the modelization of the charge exchange dynamics in a monoatomic ionized gas, and apply scattering theory to its dynamics. The free dynamics corresponds to the evolution of the total distribution of particles (neutral plus ionized particles) and the perturbed dynamics corresponds to the evolution of the neutral particles, which is the solution of a nonautonomous transport problem. The existence of the time-dependent wave operators was proved by the first author. In the present paper we follow Howland's formalism in constructing a stationary scattering theory for this nonautonomous transport problem by studying the evolution equation. We prove the existence of the wave operators and by using the smooth perturbation technique we obtain the similarity between perturbed and unperturbed operators.     

Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles

The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma.It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field E0 has also been studied in this paper.     

Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles

The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma. It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field Eo has also been studied in this paper.     

壳层纳米颗粒的光散射行为研究

本文主要研究了Au-Si球型壳层纳米颗粒在电磁波作用下的散射行为,并将其与实心Au球、空心Au球、实心Si球和空心Si球的光散射行为进行了对比。利用Mie散射理论计算得出Au-Si球型壳层纳米颗粒在外加电磁波作用下的各阶电响应和磁响应,观察壳层结构的几何参数对电偶和磁偶共振峰位置的影响,并进一步研究Au材料中的电偶响应与Si材料中的电偶(磁偶)响应之间的耦合关系,找到其中的耦合规律。通过对单个球型壳层纳米颗粒散射行为的研究,为利用该颗粒周期性排列制备具有特殊电磁性质的人工特异材料提供理论指导。     

Quark-Antiquark Bound State in Three-Dimensional Approach

International Journal of Theoretical Physics - In this paper we develop a three-dimensional approach for describing meson bound states based on the momentum-helicity basis. To this end, we...     

Four-Body Bound-State Calculations in Three-Dimensional Approach

The four-body bound state with two-body interactions is formulated in three-dimensional approach, a recently developed momentum-space representation which greatly simplifies the numerical calculations of few-body systems without performing the partial wave decomposition. The obtained three-dimensional Faddeev-Yakubovsky integral equations are solved with two-body spin-independent and spin-averaged potentials. This is the first step toward the calculations of the four-nucleon bound-state problem in three-dimensional approach. Results for four-body binding energies are in good agreement with achievements of the other methods.     

Angular Distribution of a Beam of Charged Particles Upon Multiple Scattering in Matter

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - The spectral angular distributions for charged particles of a monoenergetic beam after multiple scattering in matter is...     

Dynamic Light Scattering Measurement of Nanometer Particles in Liquids

Dynamic light scattering (DLS) techniques for studying sizes and shapes of nanoparticles in liquids are reviewed. In photon correlation spectroscopy (PCS), the time fluctuations in the intensity of light scattered by the particle dispersion are monitored. For dilute dispersions of spherical nanoparticles, the decay rate of the time autocorrelation function of these intensity fluctuations is used to directly measure the particle translational diffusion coefficient, which is in turn related to the particle hydrodynamic radius. For a spherical particle, the hydrodynamic radius is essentially the same as the geometric particle radius (including any possible solvation layers). PCS is one of the most commonly used methods for measuring radii of submicron size particles in liquid dispersions. Depolarized Fabry-Perot interferometry (FPI) is a less common dynamic light scattering technique that is applicable to optically anisotropic nanoparticles. In FPI the frequency broadening of laser light scattered by the particles is analyzed. This broadening is proportional to the particle rotational diffusion coefficient, which is in turn related to the particle dimensions. The translational diffusion coefficient measured by PCS and the rotational diffusion coefficient measured by depolarized FPI may be combined to obtain the dimensions of non-spherical particles. DLS studies of liquid dispersions of nanometer-sized oligonucleotides in a water-based buffer are used as examples.     

Fractal Character of Dynamic Light Scattering of Particles

Dynamic light scattering signals from particles, exhibit fractal characteristics. This feature can be used to determine the particle size. The use of the fractal dimension, as a quantitative method to analyze the properties of dynamic light scattering signals from submicron particles, is presented. The analysis is performed directly on the time‐resolved scattered intensity, and the Box Dimensions of light scattering signals of particles with diameters 100, 200, 500 and 1000 nm. The experimental results show that the fractal dimensions of light scattering signals correlate well with particle size. In the submicron size range, the smaller the particles, the larger their fractal dimensions. Compared with the PCS technique, only several hundreds of samples are required in the fractal method. Therefore, the data processing is easily accomplished. However, this method only provides the mean particle size, but not the particle size distribution.     

雾霾粒子的紫外光散射特性研究

紫外光与雾霾粒子发生散射后,其散射信道特性能够反映雾霾粒子的相关物理信息,利用无线紫外光单次和多次散射信道模型,采用Mie散射和T矩阵理论分析了霾粒子在不同形态和浓度下的紫外光散射信道特性,以及散射角对散射光强的影响,并完成了紫外光在雾霾环境下的实测。通过理论及仿真分析,得到了不同霾粒子形态下的紫外光通信路径损耗以及光强分布。结果表明：紫外光直视通信方式下,路径损耗随着霾粒子浓度的增大而增大,且通信质量差于晴朗天。非直视通信方式中,在短距离通信时,高霾浓度下的路径损耗小于中低霾浓度,然而随着通信距离的继续增大,高雾霾浓度下的通信质量急剧下降,低霾浓度下通信质量最终达到最优,且距离为200 m时通信质量能优于晴朗环境。当通信距离相同时,三种雾霾浓度下的紫外光散射光强分布均随着散射角的增大而减小,当散射角继续增大并超过90°时,低霾浓度下的散射光强最大。主要原因是虽然散射角继续增大,但是有效散射体体积逐渐减小,因此低霾浓度下的散射光强较大。且当粒子粒径相同时,球形粒子的衰减较非球形粒子大。雾霾环境下实测结果与仿真结果相类似,证明了仿真结果的正确性,并在一定程度上证明了实际大气中雾霾非球形粒子多于球形粒子。     

单分散系微粒的Mie散射计算

Mie散射是公认的一种极具发展前途的微粒测试技术,应用于工厂、企业排放烟尘中微粒粒度和浓度的测试,具有非接触、精度高、重复性好和可实时在线测量的优点,是研究检测污染排放的主要技术手段,也是微粒粒度和浓度分析的理论基础.本文对Mie散射理论的多个参量进行计算并给出其数学表达式.