The paper is an application of a general microscopic approach to the theory of the average scattering matrix for a particle interacting with random scatterers. We present a detailed treatment for the case of uncorrelated positions of the scatterers. First, the general two-body additive approximation is used to truncate the hierarchy of correlation functions for fluctuations. It is shown that the self-energy is accurate through the fourth power of the individual scattering amplitude. Second, the hierarchy is terminated at the next stage. The self-energy is correct to the sixth power of the scattering amplitude.Work supported in part by the National Science Foundation under Contract No. NSF DMR 79-23213. 相似文献
The statistical distribution of natural phenomena is of great significance in studying the laws of nature. In order to study the statistical characteristics of a random pulse signal, a random process model is proposed theoretically for better studying of the random law of measured results. Moreover, a simple random pulse signal generation and testing system is designed for studying the counting distributions of three typical objects including particles suspended in the air, standard particles, and background noise. Both normal and lognormal distribution fittings are used for analyzing the experimental results and testified by chi-square distribution fit test and correlation coefficient for comparison. In addition, the statistical laws of three typical objects and the relations between them are discussed in detail. The relation is also the non-integral dimension fractal relation of statistical distributions of different random laser scattering pulse signal groups. 相似文献
We present a microscopic theory of the problem of finding the properties of a particle interacting with potentials located at random sites. The sites are governed by a general probability distribution. The starting point is the multiple scattering equations for the amplitude k1|T|k2 in terms of the individual scattering amplitudes k1|T|k2. We work with quantitiesA defined by k1|T|k2=k1|T|k2exp[i(k1–k2)R]. The theory is based on a splitting of the fundamental equation forA into equations for the mean A and the fluctuationsAA. Neglect of the fluctuations yields the quasicrystalline approximation. We rearrange the equation forAA to isolate the collective part of the fluctuations. We then make the simplest microscopic truncation which is thatAA is a restricted two-body additive function of the site positions. With the contribution of the collective fluctuations, this yields results forA that are accurate to ordert4.Work supported in part by the National Science Foundation under Contract No. NSF DMRWork supported in part by the National Science Foundation under Contract No. NSF DMR 相似文献
Background, current status, and future prospects are offered for “Light scattering by Gaussian random particles: Ray-optics approximation” [1]. The stochastic geometry of the random particle is called the Gaussian random sphere. The radial distance of the Gaussian sphere is lognormally distributed. Two logarithmic radial distances at a given great-circle angle apart relate to one another according to the covariance function. Sample Gaussian particles can be conveniently generated using a Legendre polynomial expansion for the covariance function and a spherical harmonics expansion for the logarithmic radial distance. The ray-optics approximation consists of the geometric-optics and forward-diffraction parts fully accounting for polarization. It is valid for particles much larger than the wavelength of incident light and with central phase differences much larger than unity. The numerical ray-tracing algorithms are general and, in principle, applicable computationally to arbitrarily shaped non-spherical particles. 相似文献
The integrodifferential equation method is used to study the spectrum of a nanoparticle colloid for the example of interaction
of three arbitrarily arranged dielectric particles made up of nonresonant atoms (the eigenfrequency of the transition is far
from the emission frequency) with incorporated barium atoms in an external optical radiation field. The effect on the light-scattering
properties of a nanosphere in the ensemble of its distant “neighbors” is studied; an additional peak associated with them
is observed as a frequency close to the resonance for an isolated nanosphere, which under certain conditions has higher intensity
than the main peak corresponding to optical near-field resonance in a two-particle system. The dependence of the spectrum
of the nanosized system on the geometric structure is studied, and it is shown that very precise tuning of the resonance frequency
is possible by varying the angular distribution of the particles.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 641–646, September–October, 2006. 相似文献
An analytic expression of the two-frequency mutual coherence function (MCF) was derived for a two-dimensional random rough
surface. The scattered field was calculated by the Kirchhoff approximation, which is valid in the case that the radius of
curvature of the surface is much larger than the incident wave length. The scattering problem of narrowband pulse was investigated
to simplify the analytic expression of the two-frequency MCF. Numerical simulations show that the two-frequency MCF is greatly
dependent on the root-mean-square (RMS) height, while less dependent on the correlation length. The analytic solutions were
compared with the results of Monte Carlo simulation to assess the accuracy and computational efficiency.
Supported by the National Natural Science Foundation of China (Grant No. 60571058) and the National Defense Foundation of
China (Grant No. 51403020505DZ0111) 相似文献
We introduce the stochastic geometry of a Gaussian random ellipsoid (GE) and, with the discrete-dipole approximation, carry out preliminary computations for light scattering by wavelength-scale GE particles. In the GE geometry, we describe the base ellipsoid by the three semiaxes a?b?c. The axial ratios b:a and c:a appear as two shape parameters additional to those of the Gaussian random sphere geometry (GS). We compare the scattering characteristics of GE particles to those of ellipsoids. Introducing irregularities on ellipsoids smoothens the angular scattering characteristics, in a way analogous to the smoothening of spherical particle characteristics in the case of GS particles. 相似文献
Optical waveguide theory is an established part of optical physics. Yet only recently have fundamental phenomena such as spatial eigenmodes and principal modes been demonstrated experimentally. This work leverages recently developed techniques enabling detailed spatiotemporal characterisation of multimode fibre to provide new insights into the fundamentals of fibre propagation. This paper presents detailed analysis of all 420 of a fibre's principal modes and spatial eigenmodes and compares the similarity and differences between these two phenomena. It was found that even over very short lengths, the principal modes can not only significantly suppress modal dispersion but are also a more physically meaningful basis than spatial eigenmodes.
It is suggested that anomalous neutron scattering could prove a powerful experimental tool in studying ferroelectric phase
transition, the sublattice displacements of the soft modes as well as their symmetry characteristics. 相似文献
The random matrices theory is applied to a study of the heat capacity of small metallic grains. The numerical calculations indicate that the level distribution and the difference between the particles respectively with an even and an odd numbers of electrons are important for the heat capacity of the small metallic grains at a low temperature and the level correlation mainly affects the heat capacity at a high temperature. 相似文献