Hydrodynamic equations and VH light scattering from viscoelastic (solid-like and fluid-like) systems. Phenomenological approach

The dynamics of solid-like and fluid-like systems is studied whereby the expressions for the VH light scattering spectra for these systems are obtained. It is shown that for small values of k, the VH spectrum of fluid-like systems does not contain the shifted parts in contradistinction to the spectrum of the solid-like systems.     

Laser light scattering and correlation techniques for characterization of colloidal suspensions

Particle motion in colloidal suspensions causes Doppler shifts in scattered laser light. For pure diffusion, the resulting spectral broadening may be measured by intensity interferometry and photon correlation techniques. Measured line widths or decay times yield particle size information. Electrophoretic mobilities may be determined, if an electric field is applied to the suspension. However, resulting line shifts can be extremely small and real-time optical phase processing may be required to resolve it. Finally, information about particle interactions may be obtained by studying angular cross sections or by photon correlation measurements on a small number of particles, i.e. using a very small scattering volume.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

一类弱散射界面背向散射超声散斑一阶统计特性

对超声入射至分布有细小凹坑的界平面，这一类弱散射界面背向散射所形成的超声散斑的一阶统计特性进行了研究.在假设条件下，理论分析的结果表明，空间超声散斑的振幅服从Rice分布，而它们的相位概率密度函数是一个包含Gauss分布函数和Gauss概率积分函数的复合函数.当细孔密度非常大时，超声散斑的振幅就趋于Rayleigh分布.应用作者建立的由计算机控制扫描的实验系统，对这一类弱散射界面反射超声散斑的振幅分布进行了测量.实验结果表明，理论分析的结果是正确的，由此，所作的假设条件也是成立的. 关键词： 弱散射 超声散斑 统计特性     

Coherent neutron scattering by light water (H2O) and a light-heavy water mixture (64 per cent H2O/36 per cent D2O)

Measurements have been made, with high statistical accuracy, of the differential scattering cross-section for 1·06 Å neutrons by light water and a special mixture of light and heavy water at 22°C. For light water, the structure in the scattering pattern is attributed mainly to coherent scattering; a structure factor has been obtained over a limited range of momentum transfer. For the chosen mixture, the protons and deuterons give no contribution to the coherent scattering and a structure factor has been obtained which corresponds very well to the oxygen-nucleus structure factor obtained from X-ray data. The results show the desirability of extending these high accuracy measurements using isotopic substitution methods as a means of obtaining the three partial structure factors for water. The method of isotopic mixtures is applicable to a wide range of proton containing liquids.     

A review of the light scattering properties of cirrus

In this review paper the light scattering properties of naturally occurring ice crystals that are found in cirrus are discussed. Cirrus, also referred to as ice crystal clouds, due to their cold temperatures, consist of a variety of non-spherical ice particles which may take on a variety of geometrical forms. These geometrical forms can range from symmetric pristine hexagonal ice columns and plates, single bullets and bullet-rosettes to non-symmetric aggregates of these shapes. These aggregates may also consist of highly complex three-dimensional structures, which may themselves consist of symmetric components. Not only does cirrus consist of a wide variety of shapes but also sizes too, and these sizes can range between <10 μm to over 1 cm. With such a variety of shapes and sizes predicting the light scattering properties from such an ensemble of ice crystals is the current challenge. This challenge is important to overcome since with cirrus being so high in the Earth's atmosphere it has an important influence on the Earth-atmosphere radiation balance and consequently adds to the uncertainty of predicting climate change. This is why it is important to represent as accurately as possible the single-scattering properties of cirrus ice crystals within general circulation models so that uncertainties in climate change predictions can be reduced.In this review paper the current measurements and observations of ice crystal size and shape are discussed and how these observations relate to current ice crystal models is reviewed. The light scattering properties of the current ice crystal models are also discussed and it is shown how space-based instruments may be used to test these models. The need for particular microphysical and space-based measurements is stressed in order to further constrain ice crystal light scattering models.     

The dynamic angle-limited integrated scattering (DALIS) method for measuring scattering of light from optical surfaces with random roughness

A new and simple dynamic angle limited integrated scattering (DALIS) method is developed to examine optically smooth reflective surfaces with defined surface form. Our experimental results from two systems show advantages over conventional angle resolved scattering measurement (ARS) methods. By collecting scattered light in a given solid angle, our methods do not require a detection unit with an extremely large dynamic range. Unlike in the common ARS measurement method, here we use a simple linear translation stage to scan scattered light. The power spectrum density function and the autocorrelation function of the surface roughness can be recovered from the measured scattering pattern. This method can be applied to in-workshop inspection of optical polishing processes.     

Collision-induced light scattering from fluids composed of tetrahedral molecules. I

The collision-induced polarized and depolarized light scattered from fluids composed of tetrahedral molecules is examined. The correlation functions for the first-order term of the collision-induced rotational Raman effect proposed by Buckingham and Tabisz [21] are derived in the limit of binary interactions. They involve rotational correlation functions of the dipole-quadrupole polarizability, which for tetrahedral molecules is an irreducible third-rank tensor, and third-rank tensor correlation functions for relative translational motion. From a comparison of the frequency-dependent depolarization ratio of liquid carbon tetrachloride with the theoretical prediction it is concluded that also in liquids the collision-induced rotational Raman effect may contribute significantly to the depolarized spectrum for large frequency shifts.     

Static laser light scattering (SLLS) investigations of the scattering parameters of a synthetic polymer

A laser light scattering system was built to study the scattering parameters of some materials in solution form. The light source used was an argon-ion laser at wavelength 488 nm (all lines). The investigated material was a synthetic polymer which has a wide range of applications in the field of teeth medicine applications. This is polymethyl-methacrylate (PMMA) which is used for the formation of artificial clamps. The PMMA was solved in both acetone and methyl-ethyl-ketone (MEK). The acetone solvent is chosen for its high specific refractive index increment dn/dc at the same wavelength 488 nm as the argon laser source. The angular distribution of the scattered laser light intensities of PMMA dissolved in acetone was measured at different scattering angles from 30 to 150° for each concentration. The angular distributions have a symmetrical behavior about the scattering angle π/2; by using the scattered intensities the Zimm plot was formed. The weight average molecular weight (WAMW) was determined, the two other scattering parameters like as radius of gyration, h, and the second verial coefficient, A₂ were determined.     

Elastic electron scattering from C and O

Electron scattering cross sections for carbon and oxygen between q = 1 fm⁻¹ and 4 fm⁻¹ are given. The data are analysed in terms of a phenomenological charge distribution and new information concerning the tail and the center of the charge distribution are obtained. The presence of dispersion effects appears to be necessary to explain the cross sections in the first diffraction minimum. The effect of a finite potential and short range correlations on the form factor are discussed.     

Structural phase transitions in loparite‐(Ce): evidences from Raman light scattering

Raman spectroscopic studies of loparite‐(Ce), a mineral of the perovskite family, are presented. Polarized Raman spectra were obtained in the temperature range of 50–300 K. As analysis of the behavior of Raman modes showed, the temperature dependences of wavenumber, damping and intensity of the optical modes exhibited anomalies near 220 and 150 K. Softening of the low‐wavenumber modes observed in the vicinity of 150 K is interpreted as an evidence of a ferroelectric phase transition. An anisotropic quasielastic light scattering in the low‐wavenumber region of the Raman spectra was observed from 300 to 150 K. As the data suggest, loparite‐(Ce) has two structural phase transitions, one of which (at 150 K) is a ferroelectric transition of the order–disorder type. Copyright © 2014 John Wiley & Sons, Ltd.     

Broad prospects for commercial application of the ultrasonic (cavitation) melt treatment of light alloys.

Theoretical and applied aspects of ultrasonic melt treatment are considered. Industrial applications of the cavitation treatment for degassing, filtration, and grain refinement are illustrated using data for commercial alloys. Some new fields of use such as semisolid processing, low-friction alloys, and natural composites are discussed. In general, wide prospects of commercial application for the ultrasonic melt treatment of light alloys are shown.     

微小颗粒的光散射数值模拟

简单介绍了以经典Mie理论为基础的光散射测量技术在颗粒直径和颗粒浓度测量中广泛的应用。分别以Mie理论和离散偶极子近似理论(DDA)为基础, 用数值计算方法分析了球型颗粒的光散射特性，给出了微小颗粒对平行入射光散射的强度函数和散射偏振度的数值计算方法。得到了强度函数和偏振度随相关物理参量变化的三维图，为微小颗粒散射研究提供了一种三维视图。计算结果表明：当尺度参量x＜4时，2种方法所得结果差异不大；随尺度参量增大，2种方法所得结果出现较大差异。与经典Mie理论相比，由于离散偶极子近似理论可以解决各种形状的颗粒散射问题，其应用前景更广泛。     

Determination of surface roughness from light scattering measurements

We have measured the angular dependence of the p- and s-pollarized light scattered on films, which are supported by fine polished Suprasil substrates. To study the roughness of the surface we have varied the evaporation process and the thickness of the silver film. We quantitatively determine the roughness structure by using a non scalar scattering theory. The roughness structure is found in good agreement with measurements on the same films using ATR-techniques.     

Multiple light scattering from metal and dielectric rough surfaces

Abstract

A numerical study is done on light scattering from one-dimensional random rough surfaces supporting both dielectrics and metals. The influence of the corrugation on the Brewster angle as well as on the angular distribution of transmitted intensity into the dielectric is investigated. The authors also obtain enhanced backscattering in the light reflected from metallic surfaces. Finally they discuss the influence of roughness on the drop of reflectance due to polariton absorption.