气溶胶凝聚粒子散射特性的数值计算

利用Cluster-cluster aggregation (CCA)模型,模拟了由相同数目球形原始微粒凝聚而成的四种随机取向气溶胶凝聚粒子.根据物质的电结构,将气溶胶凝聚粒子离散为一系列偶极子,结合离散偶极子近似方法,在获得每一个偶极子的电偶极矩之后,数值计算了气溶胶凝聚粒子散射强度的角分布,并分析了散射强度随入射光入射角度和气溶胶凝聚粒子尺寸参数变化的规律.结果显示:当散射角较小时,气溶胶凝聚粒子取向和入射光的入射角度对散射强度影响不大,当散射角增大时,散射强度则明显依赖于气溶胶凝聚粒子取向和入射光的入射角度;对于不同尺寸参数的气溶胶凝聚粒子,在同一角度入射情况下,随尺寸参数的增加,气溶胶凝聚粒子的散射主要集中于前向散射.     

气溶胶凝聚粒子散射特性的数值计算

利用Cluster-cluster aggregation (CCA)模型,模拟了由相同数目球形原始微粒凝聚而成的四种随机取向气溶胶凝聚粒子．根据物质的电结构,将气溶胶凝聚粒子离散为一系列偶极子,结合离散偶极子近似方法,在获得每一个偶极子的电偶极矩之后,数值计算了气溶胶凝聚粒子散射强度的角分布,并分析了散射强度随入射光入射角度和气溶胶凝聚粒子尺寸参数变化的规律．结果显示：当散射角较小时,气溶胶凝聚粒子取向和入射光的入射角度对散射强度影响不大,当散射角增大时,散射强度则明显依赖于气溶胶凝聚粒子取向和入射光的入射角度;对于不同尺寸参数的气溶胶凝聚粒子,在同一角度入射情况下,随尺寸参数的增加,气溶胶凝聚粒子的散射主要集中于前向散射．     

Screening effects on polar mode scattering at high electric fields

The effects of screening of polar optical mode of scattering at high electric fields are studied by performing Monte Carlo calculations on InSb at 77 K. The average carrier energy is found to be markedly affected by the inclusion of screening.     

Space-time focusing of charged particles in radio-frequency linear electric fields

The properties of space-time focusing of nonmonoenergetic ions in linear high-frequency electric fields are studied. The degree of time focusing of ions in high-frequency fields of hyperboloidal analyzers belonging to the monopole and dipole types is estimated. The possibility of the time-of-flight mass separation of nonmonoenergetic ions in radio-frequency mass reflectors is substantiated.     

Nonlinear refractive index and light scattering due to fluctuations of molecular multipole electric fields

Statistical fluctuations of multipolar electric molecular fields, leading to variations of isotropic and anisotropic light scattering, are moreover shown to give rise to a temperature-dependent nonlinear refractive index of dense fluids. Some selected models of dipolar and quadrupolar molecules, linearly and nonlinearly polarizable and correlated in binary as well as ternary assemblages, are discussed. The formulae derived for the isotropic and anisotropic scattering constants are applicable to one-and many-component fluids, consisting of atoms and polar molecules, and provide the basis for a deeper interpretation of the latest experimental results.     

Polarization characteristics of non-Gaussian scattering by small particles

Abstract

The statistical properties of radiation which has been singly scattered by a finite number of small spheroidal particles are investigated. Single-particle fluctuation enhancement factors are calculated for a variety of incident radiation polarization states and it is shown that full probability densities can be expressed in closed form in some situations of interest. Results for both free-particle assemblies and surface deposits are presented.     

Polarization characteristics of non-Gaussian scattering by small particles

The statistical properties of radiation which has been singly scattered by a finite number of small spheroidal particles are investigated. Single-particle fluctuation enhancement factors are calculated for a variety of incident radiation polarization states and it is shown that full probability densities can be expressed in closed form in some situations of interest. Results for both free-particle assemblies and surface deposits are presented.     

基于Mie散射的带电粒子散射特性的研究

基于Mie散射研究了带电粒子的散射特性,给出散射系数与表面电导率的关系,计算了不同面电导率粒子与非带电粒子的散射角,计算表明:对金属类粒子,带电后的散射影响不大;但带电介质类粒子如水球、冰球粒子,面电荷使面电导率达到一定量级时,对散射特性有明显的影响.与水球相比,冰球的散射系数振荡现象处于粒子尺度参数更大值,振幅更强,...     

Effect of internal fields on depolarized light scattering from n-alkane gases

In this paper we extend the interacting site theory of optical response proposed by Applequist, Karl and Fung to molecules with internal degrees of freedom. We apply the theory to chain alkanes and calculate their polarizabilities. We find that the interacting site model agrees well with the experimental data on depolarized light scattering from small normal alkanes in the gas phase. Unlike the bond additive model, our model predicts the observed behaviour of the depolarization of the scattered light with the number of carbon-carbon bonds. We also discuss asymptotic behaviour of isotropic and anisotropic polarizabilities for long chains.     

Field-emission characteristics of layered systems in high electric fields

A study has been made of the field-emission characteristics of cerium and BaO films on W within a broad range of field-emission currents and fields. An anomalous broadening of the spectra and a deviation of Fowler-Nordheim characteristics from linearity have been revealed for high (above 10⁹ A/m²) field-emission current densities. The dependence of this anomalous behavior of field-emission characteristics on the work function and topography of the surface has been investigated. Possible reasons for the observed phenomena are discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 732–735 (April 1999)     

Resonant phonon scattering in quantum Hall systems driven by dc electric fields

Using dc excitation to spatially tilt Landau levels, we study resonant acoustic phonon scattering in two-dimensional electron systems. We observe that dc electric field strongly modifies phonon resonances, transforming resistance maxima into minima and back into maxima. Further, phonon resonances are enhanced dramatically in the nonlinear dc response and can be detected even at low temperatures. Most of our observations can be explained in terms of dc-induced (de)tuning of the resonant acoustic phonon scattering and its interplay with inter-Landau level impurity scattering. Finally, we observe a resistance maximum when the electron drift velocity approaches the speed of sound and a dc-induced zero-differential resistance state.     

Electromagnetic scattering of charged particles in a strong wind-blown sand electric field

Some field experimental results have shown that the moving sands or dust aerosols in nature are usually electrified,and those charged particles also produce a strong electric field in air, which is named as wind-blown sand electric field.Some scholars have pointed out that the net charge on the particle significantly enhances its electromagnetic(EM) extinction properties, but up to now, there is no conclusive research on the effect of the environmental electric field. Based on the extended Mie theory, the effect of the electric field in a sandstorm on the EM attenuation properties of the charged larger dust particle is studied. The numerical results indicate that the environmental electric field also has a great influence on the particle's optical properties, and the stronger the electric field, the bigger the effect. In addition, the charged angle, the charge density, and the particle radius all have a specific impact on the charged particle's optical properties.     

利用T-matrix计算非球形粒子散射特性的研究

本文用T-matrix方法计算了非球形气溶胶粒子的光学特性,得到了气溶胶粒子的消光截面、散射截面、吸收截面与气溶胶粒子形状的关系,不同形状气溶胶粒子的有着相同的散射相函数和不同的偏振度,非球形气溶胶粒子的散射相函数对其复折射指数的实部和虚部都不太敏感,而偏振相函数对其实部和虚部都比较敏感.此结论为研究大气辐射传输提供了较好的方法,尤其是偏振度与偏振相函数的提出为用偏振的方法进一步的反演气溶胶的光学参数提供了理论基础.     

内混合强吸收气溶胶粒子光散射的等效性

以黑碳和水两种成分组成的内混合单分散气溶胶粒子为例,根据其各消光效率因子、吸收效率因子和散射相函数,分析了用等效折射率来描述含有不同成分的内混合气溶胶系统的适用性。结果表明：在瑞利散射区和几何光学区内,内核（碳粒）体积比为0.01,0.1,0.5,0.9时,消光效率在大多数尺度参数下等效性都很好,但在米散射区内相对较差;当体积比大于0.3时,其吸收效率、消光效率等效性较好;除瑞利散射区外,散射相函数在各体积比下的等效性都很差。当考虑内混合气溶胶粒子系统的散射和吸收特性时,一般不难找到等效折射率,但在光散射技术中,应用相函数反演等效折射率的可靠性还有待商榷。     

内混合强吸收气溶胶粒子光散射的等效性

 以黑碳和水两种成分组成的内混合单分散气溶胶粒子为例,根据其各消光效率因子、吸收效率因子和散射相函数,分析了用等效折射率来描述含有不同成分的内混合气溶胶系统的适用性。结果表明：在瑞利散射区和几何光学区内,内核（碳粒）体积比为0.01,0.1,0.5,0.9时,消光效率在大多数尺度参数下等效性都很好,但在米散射区内相对较差;当体积比大于0.3时,其吸收效率、消光效率等效性较好;除瑞利散射区外,散射相函数在各体积比下的等效性都很差。当考虑内混合气溶胶粒子系统的散射和吸收特性时,一般不难找到等效折射率,但在光散射技术中,应用相函数反演等效折射率的可靠性还有待商榷。     

Coupling of massless particles to scalar fields

It is investigated whether massless particles can couple to scalar fields in a special-relativistic theory with classical particles. The only possible obvious theory which is invariant under Lorentz transformationsand reparametrization of the affine parameter leads to trivial trajectories (straight lines) for the massless case, and also the investigation of the masslesslimit of the massive theory shows that there is no influence of the scalar field on the limiting trajectories. On the other hand, in contrast to this result, it is shown that massive particlesare influence by the scalar field in this theory even in the ultrarelativistic limit.