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Mie Scattering by Ensembles of Particles with Very Large Size Parameters  [PDF]
S. Wolf,N. V. Voshchinnikov
Physics , 2004, DOI: 10.1016/j.cpc.2004.06.070
Abstract: We present a computer program for the simulation of Mie scattering in case of arbitrarily large size parameters. The elements of the scattering matrix, efficiency factors as well as the corresponding cross sections, the albedo and the scattering asymmetry parameter are calculated. Single particles as well as particle ensembles consisting of several components and particle size distributions can be considered.
Monte-Carlo-based electromagnetic modeling of nanoscale structures: accounting for inhomogeneous broadening in polydisperse ensembles  [PDF]
Herman Gudjonson,Mikhail A. Kats,Kun Liu,Zhihong Nie,Eugenia Kumacheva,Federico Capasso
Physics , 2013,
Abstract: Many experimental systems consist of large ensembles of uncoupled or weakly interacting elements operating as a single whole; this is the case in many experimental systems in nano-optics and plasmonics including colloidal solutions, plasmonic nanoparticles, dielectric resonators, antenna arrays, and others. In such experiments, measurements of the optical spectra of ensembles will differ from measurements of the independent elements even if these elements are designed to be identical as a result of small variations from element to element, known as polydispersity. In particular, sharp spectral features arising from narrow-band resonances will tend to appear broader and can even be washed out completely. Here, we explore this effect of inhomogeneous broadening as it occurs in colloidal nano-polymers comprising self-assembled nanorod chains in solution. Using a technique combining finite-difference time-domain (FDTD) simulations and Monte-Carlo sampling, we predict the inhomogeneously-broadened optical spectra of these colloidal nano-polymers, and observe significant qualitative differences compared to the unbroadened spectra. The approach combining an electromagnetic simulation technique with Monte-Carlo sampling is widely applicable for quantifying the effects of inhomogeneous broadening in a variety of physical systems, including those with many degrees of freedom which are otherwise computationally intractable.
Intercomparison Study of the CAPS PMex (Cavity Attenuated Phase Shift Particle Light Extinction Monitor) with the combination of an Integrating Nephelometer and a Particle Soot Absorption Photometer  [PDF]
A. Petzold,T. Onasch,P. Kebabian,A. Freedman
Atmospheric Measurement Techniques Discussions , 2012, DOI: 10.5194/amtd-5-7587-2012
Abstract: An evaluation of the Cavity Attenuated Phase Shift particle light extinction monitor (CAPS PMex) by means of a combination of a 3-wavelength Integrating Nephelometer (NEPH; TSI Model 3563) and a 3-wavelength filter-based Particle Soot Absorption Photometer (PSAP) was carried out using both laboratory generated test particles and ambient aerosols. An accurate determination of a fixed pathlength correction for the CAPS PMex was made by comparing extinction measurements using polystyrene latex (PSL) spheres in combination with Mie scattering calculations to account for the presence of PSL conglomerates. These studies yielded a linear instrument response over the investigated dynamical range from 20 to 450 M m 1 (10 6 m 1) with a linear correlation coefficient of R2 > 0.98. The adjustment factor was determined to be 1.05 times that previously reported. Correlating CAPS extinction to extinction measured by the NEPH-PSAP combination using laboratory-generated polydisperse mixtures of purely scattering ammonium sulfate and highly absorbing black carbon provided a linear regression line with slope m = 0.99 (R2 = 0.996) for single-scattering albedo values (λ = 630 nm) ranging from 0.35 (black carbon) to 1.00 (ammonium sulfate). For ambient aerosol, light extinction measured by CAPS PMex was highly correlated (R2 = 0.995) to extinction measured by the NEPH-PSAP combination with slope m = 0.95.
Polydisperse packings
Herrmann, H.J.;Baram, R. Mahmoodi;Wackenhut, M.;
Brazilian Journal of Physics , 2003, DOI: 10.1590/S0103-97332003000300020
Abstract: the manufacture of high resistance concrete or hard ceramics needs extremely dense granular packings. they can only be realised when the size distribution of grains is strongly polydisperse. typically powerlaw distributions give the best results. we present a simple packing model for polydisperse distributions, namely a generalized reversible parking lot model. we also discuss the perfectly dense limit, namely apollonian packings in three dimensions and show in particular the existence of space filling bearings rotating without slip and without torsion.
Polydisperse packings  [cached]
Herrmann H.J.,Baram R. Mahmoodi,Wackenhut M.
Brazilian Journal of Physics , 2003,
Abstract: The manufacture of high resistance concrete or hard ceramics needs extremely dense granular packings. They can only be realised when the size distribution of grains is strongly polydisperse. Typically powerlaw distributions give the best results. We present a simple packing model for polydisperse distributions, namely a generalized reversible parking lot model. We also discuss the perfectly dense limit, namely Apollonian packings in three dimensions and show in particular the existence of space filling bearings rotating without slip and without torsion.
Circular polarization memory in polydisperse scattering media  [PDF]
Callum M. Macdonald,Steven L. Jacques,Igor Meglinski
Physics , 2015, DOI: 10.1103/PhysRevE.91.033204
Abstract: We investigate the survival of circularly polarized light in random scattering media. The surprising persistence of this form of polarization has a known dependence on the size and refractive index of scattering particles, however a general description regarding polydisperse media is lacking. Through analysis of Mie theory, we present a means of calculating the magnitude of circular polarization memory in complex media, with total generality in the distribution of particle sizes and refractive indices. Quantification of this memory effect enables an alternate pathway towards recovering particle size distribution, based on measurements of diffusing circularly polarized light.
Wetting transitions in polydisperse fluids  [PDF]
Matteo Buzzacchi,Nigel B. Wilding,Peter Sollich
Physics , 2006, DOI: 10.1103/PhysRevLett.97.136104
Abstract: The properties of the coexisting bulk gas and liquid phases of a polydisperse fluid depend not only on the prevailing temperature, but also on the overall parent density. As a result, a polydisperse fluid near a wall will exhibit density-driven wetting transitions inside the coexistence region. We propose a likely topology for the wetting phase diagram, which we test using Monte Carlo simulations of a model polydisperse fluid at an attractive wall, tracing the wetting line inside the cloud curve and identifying the relationship to prewetting.
Comparison of porous silicon prepared using metal-induced etching (MIE) and laser-induced etching (LIE)  [PDF]
Shailendra K. Saxena,Vivek Kumar,Hari M. Rai,Gayatri Sahu,Ravi K. Late,Kapil Saxena,A. K. Shukla,Pankaj R. Sagdeo,Rajesh Kumar
Physics , 2014,
Abstract: Porous silicon (p-Si), prepared by two routes (metal induced etching (MIE) and laser induced etching (LIE)) have been studied by comparing the observed surface morphologies using SEM. A uniformly distributed smaller (submicron sized) pores are formed when MIE technique is used because the pore formation is driven by uniformly distributed metal (silver in present case) nanoparticles, deposited prior to the porosification step. Whereas in p-Si, prepared by LIE technique, wider pores with some variation in pore size as compared to MIE technique is observed because a laser having gaussian profile of intensity is used for porosification. Uniformly distribute well-aligned Si nanowires are observed in samples prepared by MIE method as seen using cross-sectional SEM imaging. A single photoluminescence (PL) peak at 1.96 eV corresponding to red emission at room temperature is observed which reveals that the Si nanowires, present in p-Si prepared by MIE, show quantum confinement effect. The single PL peak confirms the presence of uniform sized nanowires in MIE samples. These vertically aligned Si nanowires can be used for field emission application.
Freezing of Polydisperse Hard Spheres  [PDF]
N. G. Almarza,E. Enciso
Physics , 1999,
Abstract: The fluid - crystal equilibria of polydisperse mixtures of hard spheres have been studied by computer simulation of the solid phase and using an accurate equation of state for the fluid. A new scheme has been developed to evaluate the composition of crystalline phases in equilibrium with a given polydisperse fluid. Some common assumptions in theoretical approaches and their results are discussed on the light of the simulation results. Finally, no evidence of the existence of a terminal polydispersity in the fluid phase is found for polydisperse hard spheres, the disagreement of this finding with previous molecular simulation results is explained in terms of the inherent limitations of some ways of modeling the chemical potential as a function of the particle size.
Thermodynamic Limit for Polydisperse Fluids  [PDF]
S. Banerjee,R. B. Griffiths,M. Widom
Statistics , 2000,
Abstract: We examine the thermodynamic limit of fluids of hard core particles that are polydisperse in size and shape. In addition, particles may interact magnetically. Free energy of such systems is a random variable because it depends on the choice of particles. We prove that the thermodynamic limit exists with probability 1, and is independent of the choice of particles. Our proof applies to polydisperse hard-sphere fluids, colloids and ferrofluids. The existence of a thermodynamic limit implies system shape and size independence of thermodynamic properties of a system.
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