Millimeter-wave scattering from neutral and charged water droplets

We investigated 94 GHz millimeter-wave (MMW) scattering from neutral and charged water mist produced in the laboratory with an ultrasonic atomizer. Diffusion charging of the mist was accomplished with a negative ion generator (NIG). We observed increased forward- and backscattering of MMW from charged mist, as compared to MMW scattering from an uncharged mist. In order to interpret the experimental results, we developed a model based on classical electrodynamics theory of scattering from a dielectric sphere with diffusion-deposited mobile surface charge. In this approach, scattering and extinction cross-sections are calculated for a charged Rayleigh particle with effective dielectric constant consisting of the volume dielectric function of the neutral sphere and surface dielectric function due to the oscillation of the surface charge in the presence of applied electric field. For small droplets with radius smaller than 100 nm, this model predicts increased MMW scattering from charged mist, which is qualitatively consistent with the experimental observations. The objective of this work is to develop indirect remote sensing of radioactive gases via their charging action on atmospheric humid air.     

Interpretation of Light Scattering Spectra of Dispersions – A Hybrid Approach to Account for Interparticle Interactions

The problem of extracting quantitative information on individual particle properties from spectroscopic measurements conducted at concentrations where particle interactions become significant is of great industrial and theoretical importance. For dispersions of charged particles, this can happen at fairly low concentrations. The effect of the fluid (slurry) structure has to be taken into account to interpret the light scattering spectra of such dispersions. In this paper, a hybrid method that addresses the effect of the fluid structure is proposed. The hybrid approach describes the fluid structure by relating the “effective” Percus‐Yevick hard‐sphere parameters to the system parameters using empirical models. The feasibility of this approach is examined through a theoretical study with data generated by Monte Carlo simulations of a monodisperse dispersion of charged spherical particles using realistic interaction potentials under single scattering conditions.     

A Schwarzschild-like model for baryons

We present a toy model of baryons using singular solutions of the SU(2) Yang-Mill-Higgs (YMH) field equations, which bears some similarity to the Schwarzschild solution of general relativity. The SU (2) solutions are used as a background field into which a scalar, SU (2) test particle is placed. This can be compared to placing an electrically charged particle in a Coulomb background field, except the SU (2) YMH solutions are singular on a spherical membrane thus trapping (confining) the test particle inside the sphere in a manner similar to certain bag models of baryons. An interesting consequence of this model is that the composite system is a fermion even though the original Lagrangian contains only bosonic fields.     

Properties of the difference method for searching for anisotropy of primary cosmic rays

Methodical properties and features of the original difference method for searching for the anisotropy in the knee region of the primary cosmic ray energy spectrum are analyzed. It is shown that the method in which properties of particle fluxes, rather than intensities, are studied is stable to randomexperimental errors andmakes it possible to separate anomalies associatedwith the laboratory coordinate system from anomalies in the celestial coordinates. The method uses multiple scattering of charged particles in galactic magnetic fields for studying the entire celestial sphere, including sky regions beyond the installation line of sight.     

Magnetic charge,black holes,and cosmic censorship

The possibility of converting a Reissner-Nordström black hole into a naked singularity by means of test particle accretion is considered. The dually charged Reissner-Nordström metric describes a black hole only when M² > Q³ + P². The test particle equations of motion are shown to allow test particles with arbitrarily large magnetic charge/mass ratios to fall radially into electrically charged black holes. To determine the nature of the final state (black hole or naked singularity) an exact solution of Einstein's equations representing a spherical shell of magnetically charged dust falling into an electrically charged black hole is studied. Naked singularities are never formed so long as the weak energy condition is obeyed by the infalling matter. The differences between the spherical shell model and an infalling point test particle are examined and discussed.     

Isotropic Maxwell-Garnett model for biisotropic-in-biisotropic mixtures

The Rayleigh scattering response of an electrically small biisotropic sphere immersed in an ambient biisotropic medium has been utilized in constructing a Maxwell-Garnett model of a composite material formed by randomly dispersing biisotropic spheres in a biisotropic host medium. It is anticipated that this work will be of interest for estimating the electromagnetic properties of particulate media.     

Motion of a charged particle in the field of a grounded conductive sphere

Motion of a charged particle in the field of a grounded conductive sphere is investigated. It is assumed that the field created by the sphere is quasi-static that implies limitation on particle velocities by nonrelativistic values and the possibility of neglecting magnetic interaction and heat losses. A classification is provided and possible particle trajectories are constructed in the examined case.     

Light scattering by a spherical particle with multiple densely packed inclusions

This paper calculates light scattering by a spherical water particle containing densely packed inclusions at a visible wavelength 0.55 \mum by a combination of ray-tracing and Monte Carlo techniques. While the individual reflection and refraction events at the outer boundary of a sphere particle are considered by a ray-tracing program, the Monte Carlo routine simulates internal scattering processes. The main advantage of this method is that the shape of the particle can be arbitrary, and multiple scattering can be considered in the internal scattering processes. A dense-medium light-scattering theory based on the introduction of the static structure factor is used to calculate the phase function and asymmetry parameters for densely packed inclusions. Numerical results of the single scattering characteristics for a sphere containing multiple densely packed inclusions are given.     

Quasiclassical green function in an external field and small-angle scattering processes

A representation is obtained for the quasiclassical Green functions of the Dirac and Klein-Gordon equations allowing for the first nonvanishing correction in an arbitrary localized potential which generally possesses no spherical symmetry. This is used to obtain a solution of these equations in an approximation similar to the Furry-Sommerfeld-Maue approximation. It is shown that the quasiclassical Green function does not reduce to the Green function obtained in the eikonal approximation and has a wider range of validity. This is illustrated by calculating the amplitude of small-angle scattering of a charged particle and the amplitude of Delbrück forward scattering. A correction proportional to the scattering angle was obtained for the amplitude of charged particle scattering in a potential possessing no spherical symmetry. The real part of the Delbrück forward scattering amplitude was calculated in a screened Coulomb potential.     

Force exerted on a conducting spherical particle near the plate of a plane capacitor

The potential energy and the interaction force of a conducting spherical particle and a similarly charged plane plate are calculated for relatively small distances. The force is calculated from the potential energy and the plate is represented as a conducting sphere whose radius is 100 times greater than the radius of the particle. It is assumed that the particle is not charged by the plate. The domains of parameters in which the particle is always repulsed from the plate and in which the attraction takes place are determined.     

气溶胶激光散射信号的特征分析

本文应用Mie散射理论对微球体粒子光散射的性质进行了理论分析与数值计算,得出了散射光分布与微球体尺度参数、复折射率之间的关系。结果表明:不同尺度参数的粒子的散射光强的分布相差极大,随着尺度参数的增加散射光强越来越集中于前向;复折射率的变化对散射光强影响不大。并且在边界层大陆乡村型霾的气溶胶模型下对大气气溶胶的体角散射系数进行了分析与数值计算,得出:气溶胶粒子的散射光强主要分布在前向,并且随着散射角的增加有规律的减小。由此提出了利用气溶胶粒子体散射系数的性质,通过测量散射点前向散射光强和延迟时间来实现激光束的近轴定位的方法。     

Lorenz-Mie Theory for Spheres Immersed in an absorbing host medium

Light scattering by particles is often used to determine velocities or concentrations of particles in gaseous or liquid streams. Within the Lorenz-Mie theory, light scattering is well understood both for a single compact spherical particle and a single multilayered particle in a non-absorbing surrounding medium. However, in some cases of practical importance the Lorenz-Mie theory in its present form may fail to describe the scattering because the host medium is absorbing (e.g. water droplets in oil). In this case, a new treatment of the scattering theory is required. In previous work, solutions were obtained in the far-field of the scattering sphere. In this paper, a rigorous solution is derived from the calculation of the total absorption rate of the particle in the host medium, which is valid for all distances from the surface of the encapsulated particle. It is shown that it is necessary to consider finite sizes R of the integrating sphere when dealing with absorbing host media. Cross-sections are defined which are characteristic quantities not only for the particle, depending on the size of a conceptual sphere around the scatterer and the imaginary part of the refractive index of the host medium. The results obtained are discussed for the case of non-absorbing host media and in the far-field approximation. Some numerical examples are given which are also related to experimental results.     

The comparison between the Mie theory and the Rayleigh approximation to calculate the EM scattering by partially charged sand

The Mie theory and Rayleigh approximation are two basic methods to study the EM scattering of uncharged spherical particle, and when the particle radius is much smaller than the incident wavelength, they are equivalent, but whether the Rayleigh approximation is still equivalent to Mie theory when we use them to calculate the EM scattering of small charged particle, there is still no any report published to discuss this problem. In this paper we make some comparisons between Mie theory and Rayleigh approximation to solve the EM scattering of partially electrification spherical particles. The results showed that the Mie theory would be more suitable to calculate the scattering of charged spherical particles.     

A singularity-free particle model in general relativity

In general relativity a general static solution describing spherically symmetric distributions of scalar and electrically charged dust is obtained and applied to the construction of a singularity-free extended particle model.     

Arbitrary scattering of an electromagnetic zero-order Bessel beam by a dielectric sphere

Arbitrary electromagnetic (EM) scattering of a zero-order Bessel beam by a homogeneous water sphere in air is investigated. The radial components of the electric and magnetic scattering fields are expressed using a partial wave series involving the beam-shape coefficients, scattering coefficients of the sphere, and half-conical angle of the wavenumber components of the beam. The 3D scattering directivity plots in the far-field region are evaluated using a numerical integration procedure. It is shown here that shifting the sphere off the axis of wave propagation breaks the symmetry in the directivity patterns. Moreover, the scattering strongly depends on the half-cone angle of the beam. This investigation could provide a useful test of finite element codes for the evaluation of EM scattering and radiation forces, which are important in optical tweezers and related particle manipulation applications.     

Evidence for the existence of stable-water-clusters at room temperature and normal pressure

We report the finding of isolated stable-water-clusters of tens of nanometers to micron size from the evaporation of very dilute sodium chloride solution at room temperature and normal atmospheric pressure. The stable-water-clusters are found to be electrically charged by examination via an Electric Force Microscope (EFM). Raman scattering and infrared spectrum of residues from the evaporation show similar but not identical characteristics of liquid water.     

Full Action for an Electromagnetic Field with Electrical and Magnetic Charges

The paper offers the full action for an electromagnetic field with electrical and magnetic charges; Feynman laws are formulated for the calculation of the interaction cross-sections for electrically and magnetically charged particles on the base of offered action within relativistic quantum field theory. Derived with formulated Feynman rules cross-section of the interaction between an elementary particle with magnetic charge and an elementary particle with electrical charge proves to be equal zero.     

Arbitrary direction incident Gaussian beam scattering by multispheres

Based on spherical vector wave functions and their coordinate rotation theory,the field of a Gaussian beam in terms of the spherical vector wave functions in an arbitrary unparallel Cartesian coordinate system is expanded.The beam shape coefficient and its convergence property are discussed in detail.Scattering of an arbitrary direction Gaussian beam by multiple homogeneous isotropic spheres is investigated.The effects of beam waist width,sphere separation distance,sphere number,beam centre positioning,and incident angle for a Gaussian beam with two polarization modes incident on various shaped sphere clusters are numerically studied.Moreover,the scattering characteristics of two kinds of shaped red blood cells illuminated by an arbitrary direction incident Gaussian beam with two polarization modes are investigated.Our results are expected to provide useful insights into particle sizing and the measurement of the scattering characteristics of blood corpuscle particles with laser diagnostic techniques.     

S-Matrix singularities in scattering of charged particles on hydrogen-like targets

The scattering of a charged particle on an excited degenerate state of a hydrogen-like system is considered. The threshold and angular singularities of binary scattering amplitudes in this problem are studied. For these singularities closed-form analytical representations are obtained.