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Highlights • Scattering matrix of mineral dust is measured in laboratory from 176.0° to 180.0°. • A laboratory polarimeter has hence been built and validated on spherical particles. • The slopes of the scattering matrix elements tend towards zero at π-angle. • Our laboratory findings are in good agreement with T-matrix numerical code. Abstract In this paper, the scattering matrix elements of an ensemble of mineral dust particles are for the first time evaluated in laboratory for scattering angles ranging from 176.0° to the π-backscattering angle of 180.0° with a high angular resolution of 0.4° and compared with the outputs of T-matrix numerical code. Elastic light scattering is addressed at near and exact backscattering angles with a newly-built laboratory polarimeter, validated on spherical particles following the Lorenz–Mie theory. The ratios f ij (θ) = F ij (θ)/ F 11 (θ) of the scattering matrix elements of mineral dust particles are then precisely evaluated in laboratory from 176.0° up to 180.0° with a 0.4° angular resolution (even 0.2° between 179.2° and 180.0°), which is new. When approaching the π-backscattering angle, the slopes of the scattering matrix elements are almost zero, as theoretically predicted by Hovenier and Guirado [17]. Moreover, our laboratory findings are found in good agreement with the outputs of the T-matrix numerical code, showing the ability of the spheroidal model to describe light-scattering by mineral dust also from near to exact backscattering. Atmospheric implications for polarization lidar retrievals are then discussed in terms of linear and circular depolarization ratios for mineral dust. These results, which complement other existing light scattering experiments, may be used to extrapolate light scattering by mineral dust particles up the π-backscattering angle, which is useful in radiative transfer and climatology, in which backscattering is involved. [ABSTRACT FROM AUTHOR]

This study develops an idealized model to account for the effects of non-absorptive coating on the optical properties of black carbon (BC) aggregates. The classic fractal aggregate is applied to represent realistic BC particles, and the coating is assumed to be spherical. To accelerate the single-scattering simulation, BC monomers that were overlapped with coating sphere (not those completely inside the coating) are slightly moved to avoid overlapping. The multiple-sphere T-matrix method (MSTM) becomes applicable to calculate the optical properties of inhomogeneous particles with any coating amount, and is generally two orders of magnitude faster than the discrete-dipole approximation for particles we considered. Furthermore, the simple spherical coating is found to have similar effects on the optical properties to those based on more complicated coating structure. With the simple particle model and the efficient MSTM, it becomes possible to consider the influence of coating with much more details. The non-absorptive coating of BC aggregates can significantly enhance BC extinction and absorption, which is consistent with previous studies. The absorption of coated aggregates can be over two times stronger than that of BC particles without coating. Besides the coating volume, the relative position between the mass centers of BC aggregate and coating also plays an important role on the optical properties, and should obviously be considered in further studies. [ABSTRACT FROM AUTHOR]

In numerical simulations of coal combustion processes, particle-radiation interaction is often described by Mie-theory. An important modeling assumption in Mie-theory is the sphericity of the particles. The aim of this study is to investigate the validity of the sphericity assumption. Therefore, the T-Matrix method is applied to calculate the scattering and absorption properties of non-spherical particles and to compare these with results from Mie-theory. Three types of non-spherical particles are considered: prolate, oblate, and Chebychev-type particles. The scattering and absorption properties are averaged over a particle size distribution, the incident radiation profile, and for non-spherical particles a particle orientation distribution. The calculations reveal a deviation in scattering and absorption efficiencies below 10 % due to non-sphericity for all particles. For the scattering phase function, the deviation is on the order of 10 %. It strongly varies depending on the particle type under investigation. Nevertheless, Mie-theory can correctly predict trends. Taking into account several uncertainties in the input parameters for scattering calculations, Mie-theory can be applied in the prediction of scattering and absorption properties in numerical simulations of coal combustion. [ABSTRACT FROM AUTHOR]

• The linearized invariant imbedding T-matrix method is significantly improved by removing the divergent situations of original algorithms. • The derivatives associated with three kinds of effective radii are derived and shown for integrated and differential scattering properties. • The scattering properties are extremely sensitive to the aspect ratio or shape parameter under the definition of different effect radius. The Jacobians of particle scattering properties with respect to aspect ratio and effective radius (r e) using the invariant imbedding T-matrix method (IITM) are significantly improved by circumventing the divergence of derivatives. The effective radius r e is used in three definitions, which are r V , the equal-volume spherical radius, r S , the equal-surface-area spherical radius, and r VS , the ratio of three times the volume to surface area, respectively. The improved IITM and their Jacobians are applied to discuss the discrepancies between the three different definitions. The analytical Jacobians with respect to aspect ratios and effective radii associated with three effective radii are verified using the finite-difference method. Jacobians with respect to different effective radii are proportional since the ratios of different effective radii are only related to the aspect ratios. Jacobians with respect to aspect ratios are extremely sensitive to the definitions of effective radius. [ABSTRACT FROM AUTHOR]

The optical properties of diatom chains in the ocean are studied based on a combination of the many-body iterative T-matrix (MBIT) method and an improved implementation of the ray-by-ray (RBR) geometric optics method. The MBIT, a numerically accurate method, is advantageous for scatterers with linear cells. In contrast to other popular geometric optics methods, the RBR, an approximate method, considers the interference of all outgoing rays. The two methods are verified in comparison with benchmark simulations. The simulation results of diatom chains in a wide size range can be obtained with either or both methods, and each can be applied to any optically soft particle, i.e., in the case when relative refractive index approaches unity. [ABSTRACT FROM AUTHOR]

Abstract: The many-body iterative T-matrix (MBIT) method is based on the T-matrix method and focuses on scatterers with large aspect ratios. In this study, the MBIT method is extended so that it can be applied to an infinite scatterer with a 1-D periodic finite structure. A semi-analytical solution of infinite scatterers is obtained. In addition, the MBIT method is theoretically extended to include scatterers without axial rotational symmetry. The direct validation of the present method is performed by comparing the analytic solution for an infinite cylinder and the numerically accurate discrete dipole approximation method whereas indirect validation is conducted by using asymptotic solutions. Furthermore, the study also demonstrates that scattering properties of infinite scatterers can be used as a substitute for finite scatterers with large aspect ratios. [Copyright &y& Elsevier]

Abstract: A modification of the T-matrix method is proposed on the basis of the a priori information on the analytical properties of the solution. It is shown that the account for such an information allows one to obtain correct, efficient, and universal algorithms in modeling scattering characteristics for a large scale of geometries of the bodies, including essentially non-Rayleigh ones. [Copyright &y& Elsevier]

Abstract: A T-matrix solution is developed for the aim of predicting the electromagnetic scattering behaviors from a nonspherical gyroelectric particle. The theoretical treatments is implemented within the framework of the extended boundary condition method (EBCM), where a system of quasi-spherical vector wave functions (qSVWFs) for expanding electromagnetic fields inside gyroelectric media is derived by using an inverse Fourier transform operation. As verification, comparisons are made between numerical results obtained using the presented method and those published data calculated using other methods. Very good agreements are achieved for the present cases, which partially indicate the correctness of the derived theoretical formulae and the home-made program. Influences of shape deformation as well as of anisotropy components in permittivity tensor upon the scattering properties are then analyzed. Numerical results show that a dramatic decrease in radar cross sections (RCSs) level occurs when the gyroelectric cross terms are included in the permittivity tensor, and a clear shift of peaks in RCSs to smaller angles is displayed as a prolate spheroid is deformed to an oblate spheroid. [Copyright &y& Elsevier]

For a particle with rotational symmetry, the T -matrix is a powerful method for calculating the scattering properties. However, as the aspect ratio of the particle (defined as the ratio of the length of the rotational axis to the maximum dimension perpendicular to the rotational axis) deviates further from unity, the conventional T -matrix method becomes less efficient. Furthermore, when the aspect ratio is significantly large, the T -matrix algorithm diverges due to limited digital precision in numerical simulation. In this study, a many-body iterative T -matrix method (MIBT) is employed to calculate the scattering properties of a prolate particle (i.e., a particle with an aspect ratio larger than unity). The particle is divided into a number of sub-particles for which the scattering properties can be solved with the T -matrix method. The scattering properties of the original particle are acquired by adding the contributions of the artificially divided sub-particles and their interactions. Furthermore, the MBIT method is applicable to prolate particles with the sub-particles having the same or different refractive indices. [ABSTRACT FROM AUTHOR]

Abstract: Nuclear cross section calculations are often performed by using the partial wave method or the Eikonal method through Glauber theory. The expressions for the total cross section, total elastic cross section, and total reaction cross section in the partial wave method involve infinite sums and do not utilize simplifying approximations. Conversely, the Eikonal method gives these expressions in terms of integrals but utilizes the high energy and small angle approximations. In this paper, by using the fact that the partial wave component of the T-matrix can be very accurately approximated by its Born term, the infinite sums in each of the expressions for the differential cross section, total elastic cross section, total cross section, and total reaction cross section are re-written in terms of finite sums plus closed form expressions. The differential cross sections are compared to the Eikonal results for , and elastic scattering. Total cross sections, total reaction cross sections, and total elastic cross sections are compared to the Eikonal results for scattering. [Copyright &y& Elsevier]

Abstract: This paper summarizes the scientific legacy of Peter C. Waterman (1928–2012) who introduced concepts and theoretical techniques that have had a major impact on the fields of scattering by particles and particle groups, optical particle characterization, radiative transfer, and remote sensing. A biographical sketch is also included. [Copyright &y& Elsevier]

Abstract: A surface integral formulation is developed for the T matrix of a homogenous and isotropic particle of arbitrary shape, which employs scalar basis functions represented by the translation matrix elements of the vector spherical wave functions. The formulation begins with the volume integral equation for scattering by the particle, which is transformed so that the vector and dyadic components in the equation are replaced with associated dipole and multipole level scalar harmonic wave functions. The approach leads to a volume integral formulation for the T matrix, which can be extended, by the use of Green's identities, to the surface integral formulation. The result is shown to be equivalent to the traditional surface integral formulas based on the VSWF basis. [Copyright &y& Elsevier]

Abstract: Three terms, “Waterman''s T-matrix method”, “extended boundary condition method (EBCM)”, and “null field method”, have been interchangeable in the literature to indicate a method based on surface integral equations to calculate the T-matrix. Unlike the previous method, the invariant imbedding method (IIM) calculates the T-matrix by the use of a volume integral equation. In addition, the standard separation of variables method (SOV) can be applied to compute the T-matrix of a sphere centered at the origin of the coordinate system and having a maximal radius such that the sphere remains inscribed within a nonspherical particle. This study explores the feasibility of a numerical combination of the IIM and the SOV, hereafter referred to as the IIM+SOV method, for computing the single-scattering properties of nonspherical dielectric particles, which are, in general, inhomogeneous. The IIM+SOV method is shown to be capable of solving light-scattering problems for large nonspherical particles where the standard EBCM fails to converge. The IIM+SOV method is flexible and applicable to inhomogeneous particles and aggregated nonspherical particles (overlapped circumscribed spheres) representing a challenge to the standard superposition T-matrix method. The IIM+SOV computational program, developed in this study, is validated against EBCM simulated spheroid and cylinder cases with excellent numerical agreement (up to four decimal places). In addition, solutions for cylinders with large aspect ratios, inhomogeneous particles, and two-particle systems are compared with results from discrete dipole approximation (DDA) computations, and comparisons with the improved geometric-optics method (IGOM) are found to be quite encouraging. [Copyright &y& Elsevier]

Abstract: The applicability, efficiency, and accuracy of the pseudo-spectral time domain (PSTD) method are investigated with specific emphasis on the computation of the single-scattering properties of homogeneous dielectric particles. By truncating the high spectral terms, the Gibbs phenomenon is eliminated, and, consequently, the applicability of the PSTD is enhanced. The PSTD simulations for ice spheres, with moderate refractive indices and size parameters up to 200, are compared with the exact Lorenz–Mie solutions at three wavelengths. In addition, the comparison is extended to a case with an extremely large refractive index (7.150+i2.914) and size parameters up to 40. Furthermore, the single-scattering properties of randomly oriented spheroids and circular cylinders for size parameters up to 150 and 75, respectively, are calculated with the PSTD in comparison with those computed from the T-matrix method. The aspect ratio of the spheroid and the diameter-to-length ratio of the circular cylinder are 0.5 and 1, respectively. The relative errors, given by the PSTD for these randomly oriented non-spherical particles, are smaller than 2% for the extinction efficiencies and asymmetry factors and less than 30% for the phase function. The PSTD is also employed to compute the phase matrices of randomly oriented hexagonal columns with size parameters of 50 and 100. The simulations show the PSTD to be a robust method for simulating the single-scattering properties of particles with small-to-medium size parameters and for a wide range of refractive indices. [Copyright &y& Elsevier]

Abstract: Using the T-matrix approach electromagnetic scattering by a non-axisymmetric particle with an arbitrary permittivity tensor is studied. The electromagnetic fields inside the scatterer are expressed by a system of quasi-spherical vector wave functions which are derived by the use of inverse Fourier transform. Using this expansion a solution of the light scattering problem in the framework of the null-field method is obtained. The implemented T-matrix program is parallelized using both OpenMP and MPI parallel paradigms. Numerical scattering results for anisotropic ellipsoids are presented. [Copyright &y& Elsevier]

Abstract: An optical spectroscopic method is investigated theoretically for in vivo measurement of blood glucose concentration. This method is based on dynamic dual wavelength (610nm and 810nm) time-resolved measurements under a condition of artificial blood flow kinetics in a human finger. The influence of glucose concentration on absorption and reduced scattering coefficients of the whole blood is simulated using the T-matrix method. The scattering centers, RBC aggregation, under the artificial — kinetics condition are modeled as spheroid. The modified parametric slopes were derived from the Laplace transformed data of the time-resolved transmittance. The results show that an appropriate selection of the Laplace parameter can lead to enhanced sensitivity for glucose measurement. [Copyright &y& Elsevier]

Abstract: Using T-matrix method, plasmon resonance properties of metal core–shell nanoparticles are systematically investigated. It is shown that dielectric/metal core–shell structure may be excited stronger at resonance than metal/dielectric and hetero-metal ones, but the resonance states are extremely sensible to the layers thickness. For three-layer nanospheres, resonance properties will be dominated by a sub-10nm silver outermost shell, while only weakened by a silica one. Finally, tiny eccentric distance between the centers of core and shell in eccentric two-layer nanoparticles may fundamentally change the resonance mode of nanoparticles, and results in higher local electrical field enhancement than concentric nanospheres. [Copyright &y& Elsevier]

Abstract: We propose a novel approach to compute the field scattered by a particle in the near-zone, in the framework of the transition matrix formulation. This method is based on the expansion of the total near-field in terms of discrete sources vector spherical wave functions and turns out to be particularly effective to model strongly elongated or flattened particles with high permittivity. The performances are evaluated on gold spheroids with several aspect ratios. This method results very useful to understand the complex behavior of enhanced plasmon fields in resonant metallic nanostructures. [Copyright &y& Elsevier]

Abstract: We consider the scattering model in the form of a vertically and horizontally homogeneous particulate slab of an arbitrary optical thickness composed of widely separated fractal aggregates built of small spherical ice monomers. The aggregates are generated by applying three different approaches, including simulated cluster–cluster aggregation (CCA) and diffusion-limited aggregation (DLA) procedures. Having in mind radar remote-sensing applications, we report and analyze the results of computations of the backscattering circular polarization ratio obtained using efficient superposition T-matrix and vector radiative-transfer codes. The computations have been performed at a wavelength of 12.6cm for fractal aggregates with the following characteristics: monomer refractive index m=1.78+i0.003, monomer radius r=1cm, monomer packing density p=0.2, overall aggregate radii R in the range 4≤R≤10cm and fractal dimensions D f =2.5 and 3. We show that for aggregates generated with simulated CCA and DLA procedures, the respective values of the backscattering circular polarization ratio differ weakly for D f =2.5, but the differences can increase somewhat for D f =3, especially in case of an optically semi-infinite medium. For aggregates with a spheroidal overall shape, the dependence of the circular polarization ratio on the cluster morphology can be quite significant and increases with increasing the aspect ratio of the circumscribing spheroid. [Copyright &y& Elsevier]

Abstract: The effects of morphological structure, water coating, dust mixing and primary particle size distribution on the radiative properties of soot fractal aggregates in atmosphere are investigated using T-matrix method. These fractal aggregates are numerically generated using a combination of the particle–cluster and cluster–cluster aggregation algorithms with fractal parameters representing soot aggregate in atmosphere. The radiative properties of compact aggregate notably deviate from that of the branched one, and the effect of morphology changes on the radiative properties in wet air cannot be neglected. However it is reasonable to use realization-averaged radiative properties to represent that of the aggregates with certain morphology. In wet air, the scattering, absorption and extinction cross-section and symmetry parameter of soot aggregates coated with water notably increase with water shell thickness. The mixing structures of dust have little effect on radiative properties of aggregates, but the volume fraction of dust has an obvious effect on extinction, scattering and absorption cross-section of aggregates when the size parameters are above the Rayleigh limit. Although the primary particle size distribution of soot aggregate has mild effect on the scattering albedo and asymmetry parameter, the deviations of the extinction, scattering, absorption cross-section among the three size distributions are significant in this study. The size distribution has a significant effect on forward scattering of phase function, while the effect can be neglected as the size parameter approaches to the Rayleigh limit. [Copyright &y& Elsevier]

Abstract: The T-matrix method is among the most versatile, efficient, and widely used theoretical techniques for the numerically exact computation of electromagnetic scattering by homogeneous and composite particles, clusters of particles, discrete random media, and particles in the vicinity of an interface separating two half-spaces with different refractive indices. This paper presents an update to the comprehensive database of T-matrix publications compiled by us previously and includes the publications that appeared since 2007. It also lists several earlier publications not included in the original database. [Copyright &y& Elsevier]

Abstract: The method of wave function expansion is adopted to study the three dimensional scattering of a time-harmonic plane progressive sound field obliquely incident upon a multi-layered hollow cylinder with interlaminar bonding imperfection. For the generality of solution, each layer is assumed to be cylindrically orthotropic. An approximate laminate model in the context of the modal state equations with variable coefficients along with the classical T-matrix solution technique is set up for each layer to solve for the unknown modal scattering and transmission coefficients. A linear spring model is used to describe the interlaminar adhesive bonding whose effects are incorporated into the global transfer matrix by introduction of proper interfacial transfer matrices. Following the classic acoustic resonance scattering theory (RST), the scattered field and response to surface waves are determined by constructing the partial waves and obtaining the non-resonance (backgrounds) and resonance components. The solution is first used to investigate the effect of interlayer imperfection of an air-filled and water submerged bilaminate aluminium cylindrical shell on the resonances associated with various modes of wave propagation (i.e., symmetric/asymmetric Lamb waves, fluid-borne A-type waves, Rayleigh and Whispering Gallery waves) appearing in the backscattered spectrum, according to their polarization and state of stress. An illustrative numerical example is also given for a multi-layered (five-layered) cylindrical shell for which the stiffness of the adhesive interlayers is artificially varied. The sensitivity of resonance frequencies associated with higher mode numbers to the stiffness coefficients is demonstrated to be a good measure of the bonding strength. Limiting cases are considered and fair agreements with solutions available in the literature are established. [Copyright &y& Elsevier]

Abstract: The Galitskii–Migdal–Feynman (GMF) formalism is applied to spin-polarized atomic deuterium (↓D). The effective scattering length is calculated from the GMF T-matrix, which is essentially the effective scattering amplitude dependent on the medium. It is found that the S-wave effective scattering length for ↓D2 and ↓D3 varies discontinuously from negative to positive values at some critical density. This indicates a crossover from a dimer-less regime to a regime with dimers. In addition, it is confirmed that ↓D1 remains a gas down to zero Kelvin. Finally, the binding energy of the weakly bound dimers in both species ↓D2 and ↓D3 is computed. For completeness as well as for comparison purposes, the scattering length in the free-scattering limit is also calculated and it is found to be in a good agreement with previous calculations. [Copyright &y& Elsevier]

• A software for the simulation of light scattering by multiple particles near planar interfaces is presented. • The usage of the software is illustrated by several application examples. • The accuracy of the results is verified by comparison to FEM and FDTD results. • Simulations with several thousand wavelength-scale particles are feasible. SMUTHI is a python package for the efficient and accurate simulation of electromagnetic scattering by one or multiple wavelength-scale objects in a planarly layered medium. The software combines the T-matrix method for individual particle scattering with the scattering matrix formalism for the propagation of the electromagnetic field through the planar interfaces. In this article, we briefly introduce the relevant theoretical concepts and present the main features of SMUTHI. Simulation results obtained for several benchmark configurations are validated against commercial software solutions. Owing to the generality of planarly layered geometries and the availability of different particle shapes and light sources, possible applications of SMUTHI include the study of discrete random media, meta-surfaces, photonic crystals and glasses, perforated membranes and plasmonic systems, to name a few relevant examples at visible and near-visible wavelengths. [ABSTRACT FROM AUTHOR]

• Superposition T-matrix method for light scattering in periodic super cells • Avoidance of artificial periodicity induced lattice resonances • Ewald summation and plane wave coupling scheme for periodic particle grids • Derivation of spectral information from large, disordered nanostructures To model and design light propagation in disordered optical nanostructures and materials, any applicable simulation technique has to cope with enormous computational challenges in a bearable time frame. To circumvent these, the introduction of an artificial periodicity to the disordered particle structure allows to rely on computational techniques that exploit periodic boundary conditions. Choosing a rather large periodicity promises to preserve randomness in form of a close-range disorder but can introduce false interferences. So far, it remains open how the artificial periodicity has to be chosen to minimize its detrimental influence. Here, we combine the superposition T-matrix scheme with an Ewald sum formulation to account for light scattering in periodic particle arrangements that contain hundreds to thousands of individual scatterers per unit cell. Simulations reveal that the periodicity's influence cannot be minimized by simply choosing one single period much longer than the excitation wavelength. The excitation of lattice induced resonances prevents so. However, choosing a periodicity that does not sustain such detrimental features allows for reliable predictions. With that, the presented approach is suitable to derive spectral information about wave-optical phenomena in large, random particle arrangements with a spatial extend beyond those accessible with other full-wave solvers. [ABSTRACT FROM AUTHOR]

Abstract: Acoustic scattering by bounded obstacles is considered, in both two and three dimensions. Relations between the T-matrix and the far-field pattern are derived, and then used to obtain new approximations for the T-matrix for small obstacles. The problem of scattering by a pair of small sound-soft circular cylinders is also solved, in the Rayleigh approximation, using bipolar coordinates. [Copyright &y& Elsevier]

Abstract: We develop a modification of the T-matrix method that allows efficient studies of scattering properties of ensembles of independent irregular particles of different size. The advantage of the modification is quick calculations using the so-called shape-matrices (Sh-matrices), which allow more rapid calculations of scattering by particles of different size and can be used for averaging scattering properties over particle size. To illustrate the advantage we calculate the scattering-angle dependence of the intensity and degree of linear polarization of ensembles of cubes and Chebyshev particles of different size using both the new and traditional methods. Our time savings in calculating scattering properties for the particles with the new methodology is approximately a factor of ten when calculating scattering properties of one hundred of the same type of particles with different size parameter. As can be anticipated, increasing the size interval results in a smoothing of the structure of the photometric curves and a decrease in the linear polarization. [Copyright &y& Elsevier]

Abstract: Finite-difference time domain (FDTD) solutions are first compared with the corresponding T-matrix results for light scattering by circular cylinders with specific orientations. The FDTD method is then utilized to study the scattering properties of horizontally oriented hexagonal ice plates at two wavelengths, 0.55 and 12μm. The phase functions of horizontally oriented ice plates deviate substantially from their counterparts obtained for randomly oriented particles. Furthermore, we compute the phase functions of horizontally oriented ice crystal columns by using the FDTD method along with two schemes for averaging over the particle orientations. It is shown that the phase functions of hexagonal ice columns with horizontal orientations are not sensitive to the rotation about the principal axes of the particles. Moreover, hexagonal ice crystals and circular cylindrical ice particles have similar optical properties, particularly, at a strongly absorbing wavelength, if the two particle geometries have the same length and aspect ratio defined as the ratio of the radius or semi-width of the cross section of a particle to its length. The phase functions for the two particle geometries are slightly different in the case of weakly absorbing plates with large aspect ratios. However, the solutions for circular cylinders agree well with their counterparts for hexagonal columns. [Copyright &y& Elsevier]

Abstract: Simulation of light scattering gets more and more important; topics of interest are for example characterization of the shape of particles, detection of airborne fibers, determination of spherical and non-spherical particles, etc. To develop advanced methods for optical particle characterization corresponding light scattering theories and simulation programs are needed. For these kinds of simulations adequate input data representing the particle shape is important. If a specific particle shape is obtained from some reconstruction method the model will only be an approximation of the real shape. So the quality of this input particle shape has influence on the quality of the obtained results. In our research we concentrate on the development of the null-field method with discrete sources for light scattering simulation. With this method the T-matrix of complex structured particles can be computed. This paper gives an overview of solving light scattering problems with the null-field method with discrete sources and shows the influence of the accuracy of the particle shape model on the computed scattering results. [Copyright &y& Elsevier]

Abstract: This paper investigates the single-scattering properties of elongated hexagonal ice columns in random orientation. The calculation of these properties becomes more challenging with electromagnetic methods as the aspect ratio and/or the size parameter of the particles increases. The results presented in this paper have been obtained with a new version of a T-matrix implementation which uses only variables of data type real. This re-formulation makes it possible to run the code on a DEC Alpha workstation in quadruple precision. With the increased numerical precision aspect ratios of 10 are obtained at moderate size parameters. The single-scattering properties of elongated hexagonal columns are compared against those of various other particles. Circular cylinders of the same aspect ratio and surface area have quite similar single-scattering properties. They agree well in all phase matrix elements and the extinction efficiency and asymmetry parameter are within 25% and 5%, respectively. The single-scattering properties of elongated hexagonal columns are very different to those with equal surface-area and aspect ratios around unity. The extinction efficiencies of the more compact particles are several times larger than those of the elongated columns and the phase matrix elements are very different. The spheres of equal volume and equal surface area do not mimic the single-scattering properties of elongated hexagonal columns either. The agreement with the smaller sphere of equal volume-to-surface-area ratio is reasonable. It is found that for hexagonal columns with increasing aspect ratios, all phase matrix elements except the phase function converge to the Rayleigh solution. The results of this paper imply that such scattering behaviour, previously demonstrated for elongated spheroids, is more general and does also apply to faceted objects like hexagonal columns. [Copyright &y& Elsevier]

• Review on the development of generalized Lorenz-Mie theories. • Optical theorem and structured/shaped beams. • Speed of light and nature of photons regarding particular effects. • Epistemological discussion on the underdetermination thesis of theories by experiments. As the 2020 winner of the van de Hulst Award, I have been committed to the writing of a van de Hulst Essay which is presented here. The Award has been essentially motivated by my work on laser light scattering by particles, which spreads over 40 years. During this time, I may have obtained several results of interest, but some of them made me feeling this kind of extraordinary shocks, both emotional and psychological, to which it is only possible to react by a booming "Wow !". Therefore, beside a review on my work on light scattering, the heart of the present paper is devoted to 4 wow stories related to the development of generalized Lorenz-Mie theories. They concern (i) the optical theorem (ii) the speed of laser light, slower than c (iii) the speed of light spots, faster than c and (iv) the "nature" of photons. This last issue required to extend the discussion from pure scientific issues to an epistemological discussion pertaining to the philosophy of sciences. [ABSTRACT FROM AUTHOR]

• Effect of glistening characteristics on intraocular lens transmission in the eyes is analyzed from electrical point of view. • Light transmission through IOL with glistenings are calculated. • Multiple light scattering of glistenings and whitenings are applied by T-Matrix. • Light scattering simulation software, CELES (CUDA-accelerated simulation of electromagnetic scattering) is applied and studied the light transmission. Light transmission through Intraocular lens (IOL) with glistenings and whitenings are analyzed by using T-matrix theory. Visual function is decreased due to glistening and subsurface nanoglistening (whitening). Glistening means fluid-filled micro-sized vacuoles, on the other hand, whitening is nano-sized vacuoles in intraocular lens (IOL) which lead to light scattering and affect human's vision quality. Glistening observation and light scattering in IOL are observed from the characteristics of glistenings which are size, shape, refractive index and number of glistenings. When microvacuoles are densely located in IOL, light scattering for single particle is not sufficient and multiple light scattering is important to be considered. Therefore, the correlation between light transmission and glistening characteristics are investigated from electromagnetic scattering approach called T-matrix. For this purpose, light scattering simulation software, CELES (CUDA-accelerated simulation of electromagnetic scattering) is applied and studied the light transmission in terms of power reflectivity and transitivity. The simulation result can show that light transmittance through IOL to retina and evaluate the quality of the vision by light scattering. [ABSTRACT FROM AUTHOR]

• An efficient design of the realization scheme of the invariant imbedding (IIM) T-matrix light scattering model for atmospheric nonspherical particles is proposed. • The symmetric property of the U matrix is derived to improve the modeling efficiency, by which the computational time of U matrix can be cut down by over 50%. • Comprehensive comparisons are performed among the IIM T-matrix method, EBCM T-matrix method, DDASCAT, MRTD and IGOA. The invariant imbedding T-matrix method has been recognized as one of the rigorous computational tools to simulate the light scattering by atmospheric nonspherical particles after the efficient implementation by L. Bi and P. Yang. Compared with the T-matrix model based on the Extended Boundary Condition Method ("EBCM"), it is suitable for the light scattering simulation of particles with any shapes. However, since the T-matrix must be updated in each iterative process, its computational efficiency is relatively lower than EBCM, especially for the particles with large sizes and large aspect ratios. To this end, an efficient realization scheme of the IIM T-matrix method is proposed in this paper. The principle and the structure of our IIM T-matrix code is firstly introduced, and then the symmetric properties of the U-matrix (an important matrix in the IIM T-matrix method) is derived; to simplify the iteration of T-matrix calculation, the implicit matrix inversion scheme is also proposed. To validate the effectiveness of these improvements, the computational efficiency and accuracy is systematically investigated for the particles with different shapes and sizes. The simulation results indicate that the computational time is reduced notably after the model is improved by the symmetry of U-matrix and the implicit matrix inversion scheme, where for the spheroid with (a, b) = (2.5 µm, 3.0 µm) at λ=0.5 µm (the particle is treated as complex geometries without any symmetry), the computational efficiency is improved by nearly 40%. Excellent agreement is also achieved between the scattering parameters obtained by the IIM T-matrix method and the well-test scattering models (such as BECM, DDASCAT, MRTD and IGOA, etc.), indicating that the IIM T-matrix method can simulate the light scattering by nonspherical particles effectively. [ABSTRACT FROM AUTHOR]

• This compilation lists relevant T-matrix publications on electromagnetic scattering by particles and particle groups that have appeared since 2017. Since its inception in the mid-1960s, the T -matrix method has been one of the most versatile and efficient numerically exact computer solvers of the time-harmonic macroscopic Maxwell equations. It has been widely used for the computation of electromagnetic scattering by single and composite particles, discrete random media, periodic structures (including metamaterials), and particles in the vicinity of plane or rough interfaces separating media with different refractive indices. This compilation is the ninth update to the comprehensive thematic database of peer-reviewed T -matrix publications initiated in 2004 and lists relevant publications that have appeared since 2017. It also includes a few earlier publications that have so far been overlooked. [ABSTRACT FROM AUTHOR]

Abstract: We adopt a T-matrix approach to study quarkonium properties and heavy-quark transport in a Quark-Gluon Plasma. The T-matrix approach is well suited to implement potential scattering and thus provides a common framework for low-momentum transfer interactions in heavy-heavy and heavy-light quark systems. We assume that the underlying potentials can be estimated from the heavy-quark free energy computed in lattice QCD. We discuss constraints from vacuum spectroscopy, uncertainties arising from different choices of the potential, and the role of elastic and inelastic widths which are naturally accounted for in the T-matrix formalism. [Copyright &y& Elsevier]