Mie Scattering
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In
electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...
, the Mie solution to
Maxwell's equations Maxwell's equations, or Maxwell–Heaviside equations, are a set of coupled partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, Electrical network, electr ...
(also known as the Lorenz–Mie solution, the Lorenz–Mie–Debye solution or Mie scattering) describes the
scattering In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiat ...
of an electromagnetic
plane wave In physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of ...
by a homogeneous
sphere A sphere (from Ancient Greek, Greek , ) is a surface (mathematics), surface analogous to the circle, a curve. In solid geometry, a sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...
. The solution takes the form of an
infinite series In mathematics, a series is, roughly speaking, an addition of infinitely many terms, one after the other. The study of series is a major part of calculus and its generalization, mathematical analysis. Series are used in most areas of mathemati ...
of spherical multipole partial waves. It is named after German physicist Gustav Mie. The term ''Mie solution'' is also used for solutions of Maxwell's equations for scattering by stratified spheres or by infinite cylinders, or other geometries where one can write separate equations for the radial and angular dependence of solutions. The term ''Mie theory'' is sometimes used for this collection of solutions and methods; it does not refer to an independent physical theory or law. More broadly, the "Mie scattering" formulas are most useful in situations where the size of the scattering particles is comparable to the wavelength of the light, rather than much smaller or much larger. Mie scattering (sometimes referred to as a non-molecular scattering or aerosol particle scattering) takes place in the lower of the
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
, where many essentially spherical particles with diameters approximately equal to the wavelength of the incident ray may be present. Mie scattering theory has no upper size limitation, and converges to the limit of geometric optics for large particles.


Introduction

A modern formulation of the Mie solution to the scattering problem on a sphere can be found in many books, e.g., J. A. Stratton's ''Electromagnetic Theory''. In this formulation, the incident plane wave, as well as the scattering field, is expanded into radiating spherical vector spherical harmonics. The internal field is expanded into regular vector spherical harmonics. By enforcing the
boundary condition In the study of differential equations, a boundary-value problem is a differential equation subjected to constraints called boundary conditions. A solution to a boundary value problem is a solution to the differential equation which also satis ...
on the spherical surface, the expansion coefficients of the scattered field can be computed. For particles much larger or much smaller than the wavelength of the scattered light there are simple and accurate approximations that suffice to describe the behavior of the system. But for objects whose size is within a few orders of magnitude of the wavelength, e.g., water droplets in the atmosphere, latex particles in paint, droplets in emulsions, including milk, and biological cells and cellular components, a more detailed approach is necessary. The Mie solution is named after its developer, German physicist Gustav Mie. Danish physicist Ludvig Lorenz and others independently developed the theory of electromagnetic plane wave scattering by a
dielectric In electromagnetism, a dielectric (or dielectric medium) is an Insulator (electricity), electrical insulator that can be Polarisability, polarised by an applied electric field. When a dielectric material is placed in an electric field, electric ...
sphere. The formalism allows the calculation of the electric and magnetic fields inside and outside a spherical object and is generally used to calculate either how much light is scattered (the total optical cross section), or where it goes (the form factor). The notable features of these results are the Mie resonances, sizes that scatter particularly strongly or weakly. This is in contrast to
Rayleigh scattering Rayleigh scattering ( ) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scat ...
for small particles and Rayleigh–Gans–Debye scattering (after Lord Rayleigh, Richard Gans and
Peter Debye Peter Joseph William Debye ( ; born Petrus Josephus Wilhelmus Debije, ; March 24, 1884 – November 2, 1966) was a Dutch-American physicist and physical chemist, and Nobel laureate in Chemistry. Biography Early life Born in Maastricht, Neth ...
) for large particles. The existence of resonances and other features of Mie scattering makes it a particularly useful formalism when using scattered light to measure particle size.


Approximations


Rayleigh approximation (scattering)

Rayleigh scattering describes the elastic scattering of light by spheres that are much smaller than the wavelength of light. The intensity ''I'' of the scattered radiation is given by : I = I_0 \left( \frac \right) \left( \frac \right)^4 \left(\frac \right)^2 \left( \frac \right)^6, where ''I0'' is the light intensity before the interaction with the particle, ''R'' is the distance between the particle and the observer, ''θ'' is the scattering angle, ''λ'' is the wavelength of light under consideration, ''n'' is the
refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
of the particle, and ''d'' is the diameter of the particle. It can be seen from the above equation that Rayleigh scattering is strongly dependent upon the size of the particle and the wavelengths. The intensity of the Rayleigh scattered radiation increases rapidly as the ratio of particle size to wavelength increases. Furthermore, the intensity of Rayleigh scattered radiation is identical in the forward and reverse directions. The Rayleigh scattering model breaks down when the particle size becomes larger than around 10% of the wavelength of the incident radiation. In the case of particles with dimensions greater than this, Mie's scattering model can be used to find the intensity of the scattered radiation. The intensity of Mie scattered radiation is given by the summation of an infinite series of terms rather than by a simple mathematical expression. It can be shown, however, that scattering in this range of particle sizes differs from Rayleigh scattering in several respects: it is roughly independent of wavelength and it is larger in the forward direction than in the reverse direction. The greater the particle size, the more of the light is scattered in the forward direction. The blue colour of the sky results from Rayleigh scattering, as the size of the gas particles in the atmosphere is much smaller than the wavelength of visible light. Rayleigh scattering is much greater for blue light than for other colours due to its shorter wavelength. As sunlight passes through the atmosphere, its blue component is Rayleigh scattered strongly by atmospheric gases but the longer wavelength (e.g. red/yellow) components are not. The sunlight arriving directly from the Sun therefore appears to be slightly yellow, while the light scattered through rest of the sky appears blue. During sunrises and sunsets, the effect of Rayleigh scattering on the spectrum of the transmitted light is much greater due to the greater distance the light rays have to travel through the high-density air near the Earth's surface. In contrast, the water droplets that make up clouds are of a comparable size to the wavelengths in visible light, and the scattering is described by Mie's model rather than that of Rayleigh. Here, all wavelengths of visible light are scattered approximately identically, and the clouds therefore appear to be white or grey.


Rayleigh–Gans approximation

The Rayleigh–Gans approximation is an approximate solution to light scattering when the relative refractive index of the particle is close to that of the environment, and its size is much smaller in comparison to the wavelength of light divided by , ''n'' − 1, , where ''n'' is the
refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
: :\begin , n - 1, &\ll 1 \\ kd, n - 1, &\ll 1 \end where k is the wavevector of the light (k=\frac), and d refers to the linear dimension of the particle. The former condition is often referred as ''optically soft'' and the approximation holds for particles of arbitrary shape.


Anomalous diffraction approximation of van de Hulst

The anomalous diffraction approximation is valid for large (compared to wavelength) and optically soft spheres; soft in the context of optics implies that the refractive index of the particle (m) differs only slightly from the refractive index of the environment, and the particle subjects the wave to only a small phase shift. The extinction efficiency in this approximation is given by : Q = 2 - \frac \sin p + \frac (1 - \cos p), where ''Q'' is the efficiency factor of scattering, which is defined as the ratio of the scattering cross-section and geometrical cross-section π''a''2. The term ''p'' = 4πa(''n'' − 1)/λ has as its physical meaning the phase delay of the wave passing through the centre of the sphere, where ''a'' is the sphere radius, ''n'' is the ratio of refractive indices inside and outside of the sphere, and ''λ'' the wavelength of the light. This set of equations was first described by van de Hulst in (1957).


Mathematics

The scattering by a spherical
nanoparticle A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At ...
is solved exactly regardless of the particle size. We consider scattering by a plane wave propagating along the ''z''-axis polarized along the ''x''-axis. Dielectric and magnetic permeabilities of a particle are \varepsilon_1 and \mu_1, and \varepsilon and \mu for the environment. In order to solve the scattering problem, we write first the solutions of the vector
Helmholtz equation In mathematics, the Helmholtz equation is the eigenvalue problem for the Laplace operator. It corresponds to the elliptic partial differential equation: \nabla^2 f = -k^2 f, where is the Laplace operator, is the eigenvalue, and is the (eigen)fun ...
in spherical coordinates, since the fields inside and outside the particles must satisfy it. Helmholtz equation: : \nabla^ \mathbf + ^ \mathbf = 0, \quad \nabla^ \mathbf + ^ \mathbf = 0. In addition to the Helmholtz equation, the fields must satisfy the conditions \nabla \cdot \mathbf=\nabla \cdot \mathbf=0 and \nabla \times \mathbf=i \omega\mu \mathbf, \nabla \times \mathbf=-i \omega\varepsilon \mathbf. Vector spherical harmonics possess all the necessary properties, introduced as follows: : \mathbf_=\nabla \times\left(\mathbf \psi_\right)  — magnetic harmonics (TE), : \mathbf_=\frac  — electric harmonics (TM), where : : and P_^(\cos \theta) —
Associated Legendre polynomials In mathematics, the associated Legendre polynomials are the canonical solutions of the general Legendre equation \left(1 - x^2\right) \frac P_\ell^m(x) - 2 x \frac P_\ell^m(x) + \left \ell (\ell + 1) - \frac \rightP_\ell^m(x) = 0, or equivalently ...
, and z_( r)  — any of the spherical Bessel functions. Next, we expand the incident plane wave in vector spherical harmonics: : \begin \mathbf_ &= E_0e^\mathbf_x=E_\sum_^ i^n\frac\left( \mathbf^_(k, \mathbf)-i \mathbf_^(k, \mathbf)\right), \\ \mathbf_ &= \fracE_\sum_^ i^n\frac\left( \mathbf^_(k, \mathbf)+i \mathbf_^(k, \mathbf)\right). \end Here the superscript (1) means that in the radial part of the functions \psi_ are spherical Bessel functions of the first kind. The expansion coefficients are obtained by taking integrals of the form : \frac. In this case, all coefficients at m\neq 1 are zero, since the integral over the angle \varphi in the numerator is zero. Then the following conditions are imposed: # Interface conditions on the boundary between the sphere and the environment (which allow us to relate the expansion coefficients of the incident, internal, and scattered fields) # The condition that the solution is bounded at the origin (therefore, in the radial part of the generating functions \psi_, spherical Bessel functions of the first kind are selected for the internal field), # For a scattered field, the asymptotics at infinity corresponds to a diverging spherical wave (in connection with this, for the scattered field in the radial part of the generating functions \psi_ spherical Hankel functions of the first kind are chosen). Scattered fields are written in terms of a vector harmonic expansion as : \mathbf_=\sum_^ E_\left(i a_ \mathbf_^(k, \mathbf)-b_ \mathbf_^(k, \mathbf)\right), : \mathbf_=\frac\sum_^ E_\left(a_ \mathbf_^(k, \mathbf)+ib_ \mathbf_^(k, \mathbf)\right). Here the superscript (3) means that in the radial part of the functions \psi_ are spherical Hankel functions of the first kind (those of the second kind would have (4)), and E_n= \frac, Internal fields: : \mathbf_=\sum_^ E_\left(-i d_ \mathbf_^(k_1, \mathbf)+c_ \mathbf_^(k_1, \mathbf)\right), : \mathbf_=\frac\sum_^ E_\left(d_ \mathbf_^(k_1, \mathbf)+ic_ \mathbf_^(k_1, \mathbf)\right). k = \fracn is the wave vector outside the particle k_1 = \frac  is the wave vector in the medium from the particle material, n and n_1 are the refractive indices of the medium and the particle. After applying the interface conditions, we obtain expressions for the coefficients: : c_n(\omega) = \frac , : d_n(\omega) = \frac , : b_n(\omega) = \frac , : a_n(\omega) = \frac , where :\rho=ka, :\rho_1=k_1a with a being the radius of the sphere. j_n and h_n represent the spherical functions of Bessel and Hankel of the first kind, respectively.


Scattering and extinction cross-sections

Values commonly calculated using Mie theory include efficiency coefficients for
extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
Q_e,
scattering In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiat ...
Q_s, and absorption Q_a. These efficiency coefficients are ratios of the cross section of the respective process, \sigma_i, to the particle protected area, Q_i = \frac , where ''a'' is the particle radius. According to the definition of extinction, : \sigma_e = \sigma_s + \sigma_a and Q_e = Q_s + Q_a . The scattering and extinction coefficients can be represented as the infinite series: :Q_s = \frac\sum_^\infty (2n + 1)\left(, a_, ^2 + , b_, ^2\right) :Q_e = \frac\sum_^\infty (2n + 1)\Re(a_ + b_) The contributions in these sums, indexed by ''n'', correspond to the orders of a
multipole expansion A multipole expansion is a mathematical series representing a function that depends on angles—usually the two angles used in the spherical coordinate system (the polar and azimuthal angles) for three-dimensional Euclidean space, \R^3. Multipo ...
with being the dipole term, being the quadrupole term, and so forth.


Application to larger particles

If the size of the particle is equal to several wavelengths in the material, then the scattered fields have some features. Further, the form of the electric field is key, since the magnetic field is obtained from it by taking the
curl cURL (pronounced like "curl", ) is a free and open source computer program for transferring data to and from Internet servers. It can download a URL from a web server over HTTP, and supports a variety of other network protocols, URI scheme ...
. All Mie coefficients depend on the frequency and have maximums when the denominator is close to zero (exact equality to zero is achieved for complex frequencies). In this case, it is possible, that the contribution of one specific harmonic dominates in scattering. Then at large distances from the particle, the
radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: " ...
of the scattered field will be similar to the corresponding radiation pattern of the angular part of vector spherical harmonics. The harmonics \mathbf_ correspond to electric dipoles (if the contribution of this harmonic dominates in the expansion of the electric field, then the field is similar to the electric dipole field), \mathbf_ correspond to the electric field of the magnetic dipole, \mathbf_ and \mathbf_ - electric and magnetic quadrupoles, \mathbf_ and \mathbf_ - octupoles, and so on. The maxima of the scattering coefficients (as well as the change of their phase to \pi ) are called multipole resonances, and zeros can be called anapoles. The dependence of the scattering cross-section on the wavelength and the contribution of specific resonances strongly depends on the particle material. For example, for a gold particle with a radius of 100 nm, the contribution of the electric dipole to scattering predominates in the optical range, while for a
silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
particle there are pronounced magnetic dipole and quadrupole resonances. For metal particles, the peak visible in the scattering cross-section is also called localized plasmon resonance. In the limit of small particles or long wavelengths, the electric dipole contribution dominates in the scattering cross-section.


Other directions of the incident plane wave

In case of ''x-''polarized plane wave, incident along the ''z''-axis, decompositions of all fields contained only harmonics with ''m''= 1, but for an arbitrary incident wave this is not the case. For a rotated plane wave, the expansion coefficients can be obtained, for example, using the fact that during rotation, vector spherical harmonics are transformed through each other by Wigner D-matrixes. In this case, the scattered field will be decomposed by all possible harmonics: : \mathbf_s = \sum_^\infty \sum_^n E_0( D_ \mathbf_^(k,\mathbf)+ D_ \mathbf_^(k,\mathbf)+ D_ \mathbf_^(k,\mathbf)+ D_ \mathbf_^(k,\mathbf)) Then the scattering cross section will be expressed in terms of the coefficients as follows: : \begin C_ = \frac \sum_^\infty \frac &\times \left D_, ^2 + , D_, ^2 + , D_, ^2 + , D_, ^2 \right) \right. \\ &+ \left.\vphantom 2, D_, ^2 + 2, D_, ^2 \right \end


Kerker effect

The ''Kerker effect'' is a phenomenon in scattering directionality, which occurs when different multipole responses are presented and not negligible. In 1983, in the work of Kerker, Wang and Giles, the direction of scattering by particles with \mu \neq 1 was investigated. In particular, it was shown that for hypothetical particles with \mu = \varepsilon backward scattering is completely suppressed. This can be seen as an extension to a spherical surface of Giles' and Wild's results for reflection at a planar surface with equal refractive indices where reflection and transmission is constant and independent of angle of incidence. In addition, scattering cross sections in the forward and backward directions are simply expressed in terms of Mie coefficients: : \begin C_^\text &= \frac\left, \sum_^\infty (-1)^n(a_n - b_n)\^2 \\ C_^\text &= \frac\left, \sum_^\infty (a_n + b_n)\^2 \end For certain combinations of coefficients, the expressions above can be minimized. So, for example, when terms with n>1 can be neglected ( dipole approximation), (a_1 - b_1) = 0 , corresponds to the minimum in backscattering (magnetic and electric dipoles are equal in magnitude and are in phase, this is also called ''first Kerker'' or ''zero-backward intensity condition''). And (a_1 + b_1) = 0 corresponds to minimum in forward scattering, this is also called ''second Kerker condition'' (or ''near-zero forward intensity condition''). From the optical theorem, it is shown that for a passive particle (a_1=-b_1) is not possible. For the exact solution of the problem, it is necessary to take into account the contributions of all multipoles. The sum of the electric and magnetic dipoles forms Huygens source For dielectric particles, maximum forward scattering is observed at wavelengths longer than the wavelength of magnetic dipole resonance, and maximum backward scattering at shorter ones. Later, other varieties of the effect were found. For example, the transverse Kerker effect, with nearly complete simultaneous suppression of both forward and backward scattered fields (side-scattering patterns), optomechanical Kerker effect, in acoustic scattering, and also found in plants. There is also a short with an explanation of the effect.


Dyadic Green's function of a sphere

Green's function In mathematics, a Green's function (or Green function) is the impulse response of an inhomogeneous linear differential operator defined on a domain with specified initial conditions or boundary conditions. This means that if L is a linear dif ...
is a solution to the following equation: : \nabla\times\nabla\times (\omega,\mathbf,\mathbf') = \left(\frac\right)^\varepsilon(\mathbf, \omega)(\omega,\mathbf,\mathbf')+ \delta(\mathbf - \mathbf'), where \hat — identity matrix \varepsilon(\mathbf, \omega) = \varepsilon_ (\omega) for r < a, and \varepsilon(\mathbf, \omega) = \varepsilon for r > a. Since all fields are vectorial, the Green function is a 3 by 3 matrix and is called a dyadic. If polarization \mathbf(\mathbf) is induced in the system, when the fields are written as : \mathbf^() = \omega^2\mu\int\limits_V \textV' \hat (,k) \mathbf^ (\mathbf') In the same way as the fields, the Green's function can be decomposed into vector spherical harmonics. Dyadic Green's function of a free space a: : \begin &\hat ^0() \\ = &\frac\delta(\mathbf - \mathbf') + \frac \sum_^ \sum_^n (2 - \delta_) \frac \frac \cdot \\ &\quad \begin \begin\left(\left(\mathbf_^ , \mathbf\otimes^_ , \mathbf'right.\right. &+\left.\left.\mathbf_^ , \mathbf\otimes^_ , \mathbf'right)\right. \\ &+\left.\left(_^ ,\mathbf\otimes ^_ , \mathbf' +\mathbf_^ , \mathbf\otimes ^_ , \mathbf'right) \right) \end &\text r < r' \\ \begin\left(\left(\mathbf_^ , \mathbf\otimes^_ , \mathbf'right.\right. &+\left.\left.\mathbf_^ , \mathbf\otimes ^_ , \mathbf'right)\right. \\ &+\left.\left(_^ ,\mathbf\otimes ^_ , \mathbf' +\mathbf_^ , \mathbf\otimes ^_ , \mathbf'right) \right) \end &\text r > r' \end \end In the presence of a sphere, the Green's function is also decomposed into vector spherical harmonics. Its appearance depends on the environment in which the points \mathbf and \mathbf' are located. When both points are outside the sphere (r > a, r' > a): : \begin &\hat^() \\ = &\hat^0() + \frac \sum_^ \sum_^n (2 - \delta_) \frac \frac \cdot \\ &\quad \left( a_n^(\omega)\left(\mathbf_^ , \mathbf\otimes ^_ , \mathbf'right) + b_n^(\omega)\left(_^ , \mathbf\otimes ^_ , \mathbf'right)\right) \end where the coefficients are : : \begin a_n^(\omega) &= \frac , \\ b_n^(\omega) &= \frac . \end When both points are inside the sphere (r < a, r' < a) : : \begin &\hat ^() \\ = &\hat ^0() + \frac \sum_^ \sum_^n (2 - \delta_) \frac \frac \cdot \\ &\quad \left( c_n^(\omega) \left(\mathbf_^ _1, \mathbf\otimes ^_ _1, \mathbf'right) + d_n^(\omega)\left(_^ _1, \mathbf\otimes ^_ _1, \mathbf'right)\right), \end Coefficients: : \begin c_n^(\omega) &= \frac , \\ d_n^(\omega) &= \frac . \end Source is inside the sphere and observation point is outside (r > a, r' < a): : \begin &\hat^() \\ = &\frac \sum_^ \sum_^n (2-\delta_) \frac \frac \cdot \\ &\quad \left( a_n^(\omega) (\mathbf_^ , \mathbf\otimes ^_ _1, \mathbf' + b_n^(\omega)\left(\mathbf_^ , \mathbf\otimes ^_ _1, \mathbf'right)\right) \end coefficients: : \begin a_n^(\omega) &= \frac , \\ b_n^(\omega) &= \frac . \end Source is outside the sphere and observation point is inside (ra) : : \begin &\hat^() \\ = &\frac \sum_^ \sum_^n (2 - \delta_) \frac \frac \cdot \\ &\quad \left( c_n^(\omega) (\mathbf_^ , \mathbf\otimes ^_ _1, \mathbf' + d_n^(\omega)(_^ , \mathbf\otimes ^_ _1, \mathbf'\right) \end coefficients: : \begin c_n^(\omega) &= \frac, \\ d_n^(\omega) &= \frac. \end


Computational codes

Mie solutions are implemented in a number of programs written in different computer languages such as Fortran,
MATLAB MATLAB (an abbreviation of "MATrix LABoratory") is a proprietary multi-paradigm programming language and numeric computing environment developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementat ...
, and
Mathematica Wolfram (previously known as Mathematica and Wolfram Mathematica) is a software system with built-in libraries for several areas of technical computing that allows machine learning, statistics, symbolic computation, data manipulation, network ...
. These solutions approximate an infinite series, and provide as output the calculation of the scattering phase function, extinction, scattering, and absorption efficiencies, and other parameters such as asymmetry parameters or radiation torque. Current usage of the term "Mie solution" indicates a series approximation to a solution of Maxwell's equations. There are several known objects that allow such a solution: spheres, concentric spheres, infinite cylinders, clusters of spheres and clusters of cylinders. There are also known series solutions for scattering by ellipsoidal particles. A list of codes implementing these specialized solutions is provided in the following: *
Codes for electromagnetic scattering by spheres Codes for electromagnetic scattering by spheres - this article list codes for electromagnetic scattering by a homogeneous sphere, layered sphere, and cluster of spheres. Solution techniques Majority of existing codes for calculation of electromagn ...
– solutions for a single sphere, coated spheres, multilayer sphere, and cluster of spheres; *
Codes for electromagnetic scattering by cylinders Codes for electromagnetic scattering by cylinders – this article list codes for electromagnetic scattering by a cylinder. Majority of existing codes for calculation of electromagnetic scattering by a single cylinder are based on Mie theory, which ...
– solutions for a single cylinder, multilayer cylinders, and cluster of cylinders. A generalization that allows a treatment of more generally shaped particles is the T-matrix method, which also relies on a series approximation to solutions of Maxwell's equations. See also
external links An internal link is a type of hyperlink on a web page to another page or resource, such as an image or document, on the same website or domain. It is the opposite of an external link, a link that directs a user to content that is outside its d ...
for other codes and calculators.


Applications

Mie theory is very important in
meteorological Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agriculture ...
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...
, where diameter-to-wavelength ratios of the order of unity and larger are characteristic for many problems regarding haze and
cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
scattering. A further application is in the characterization of
particles In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from s ...
by optical scattering measurements. The Mie solution is also important for understanding the appearance of common materials like
milk Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals (including breastfeeding, breastfed human infants) before they are able to digestion, digest solid food. ...
,
biological tissue In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. Tissues occupy a biological organizational level between cells and a complete or ...
and
latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latices are found in nature, but synthetic latices are common as well. In nature, latex is found as a wikt:milky, milky fluid, which is present in 10% of all floweri ...
paint.


Atmospheric science

Mie scattering occurs when the diameters of atmospheric
particulates Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspension (chemistry), suspended in the atmosphere of Earth, air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate ...
are similar to or larger than the wavelengths of the light.
Dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...
,
pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
,
smoke Smoke is an aerosol (a suspension of airborne particulates and gases) emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwante ...
and microscopic
water droplets Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms ( ...
that form
cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
s are common causes of Mie scattering. Mie scattering occurs mostly in the lower portions of the atmosphere, where larger particles are more abundant, and dominates in cloudy conditions.


Cancer detection and screening

Mie theory has been used to determine whether scattered light from tissue corresponds to healthy or cancerous cell nuclei using
angle-resolved low-coherence interferometry Angle-resolved low-coherence interferometry (a/LCI) is an emerging biomedical imaging technology which uses the properties of scattered light to measure the average size of cell structures, including cell nuclei. The technology shows promise as ...
.


Clinical laboratory analysis

Mie theory is a central principle in the application of nephelometric based assays, widely used in medicine to measure various plasma proteins. A wide array of plasma proteins can be detected and quantified by nephelometry.


Magnetic particles

A number of unusual electromagnetic scattering effects occur for magnetic spheres. When the
relative permittivity The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the vacuum permittivity, electric permittivity of a vacuum. A dielectric is an insulating material, and the dielectric co ...
equals the permeability, the back-scatter gain is zero. Also, the scattered radiation is polarized in the same sense as the incident radiation. In the small-particle (or long-wavelength) limit, conditions can occur for zero forward scatter, for complete polarization of scattered radiation in other directions, and for asymmetry of forward scatter to backscatter. The special case in the small-particle limit provides interesting special instances of complete polarization and forward-scatter-to-backscatter asymmetry.


Metamaterial

Mie theory has been used to design
metamaterial A metamaterial (from the Greek word μετά ''meta'', meaning "beyond" or "after", and the Latin word ''materia'', meaning "matter" or "material") is a type of material engineered to have a property, typically rarely observed in naturally occu ...
s. They usually consist of three-dimensional composites of metal or non-metallic inclusions periodically or randomly embedded in a low-permittivity matrix. In such a scheme, the negative constitutive parameters are designed to appear around the Mie resonances of the inclusions: the negative effective
permittivity In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter (epsilon), is a measure of the electric polarizability of a dielectric material. A material with high permittivity polarizes more ...
is designed around the resonance of the Mie electric dipole scattering coefficient, whereas negative effective permeability is designed around the resonance of the Mie magnetic dipole scattering coefficient, and doubly negative material (DNG) is designed around the overlap of resonances of Mie electric and magnetic dipole scattering coefficients. The particle usually have the following combinations: # one set of magnetodielectric particles with values of relative permittivity and permeability much greater than one and close to each other; # two different dielectric particles with equal permittivity but different size; # two different dielectric particles with equal size but different permittivity. In theory, the particles analyzed by Mie theory are commonly spherical but, in practice, particles are usually fabricated as cubes or cylinders for ease of fabrication. To meet the criteria of homogenization, which may be stated in the form that the lattice constant is much smaller than the operating wavelength, the relative permittivity of the dielectric particles should be much greater than 1, e.g. \varepsilon_\text > 78(38) to achieve negative effective permittivity (permeability).


Particle sizing

Mie theory is often applied in laser diffraction analysis to inspect the particle sizing effect. While early computers in the 1970s were only able to compute diffraction data with the more simple Fraunhofer approximation, Mie is widely used since the 1990s and officially recommended for particles below 50 micrometers in guideline ISO 13320:2009. Mie theory has been used in the detection of oil concentration in polluted water. Mie scattering is the primary method of sizing single sonoluminescing bubbles of air in water and is valid for cavities in materials, as well as particles in materials, as long as the surrounding material is essentially non-absorbing.


Parasitology

It has also been used to study the structure of ''
Plasmodium falciparum ''Plasmodium falciparum'' is a Unicellular organism, unicellular protozoan parasite of humans and is the deadliest species of ''Plasmodium'' that causes malaria in humans. The parasite is transmitted through the bite of a female ''Anopheles'' mos ...
'', a particularly pathogenic form of
malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...
.


Extensions

In 1986, P. A. Bobbert and J. Vlieger extended the Mie model to calculate scattering by a sphere in a homogeneous medium placed on flat surface: the Bobbert–Vlieger (BV) model. Like the Mie model, the extended model can be applied to spheres with a radius nearly the wavelength of the incident light. The model has been implemented in C++
source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...
. Recent developments are related to scattering by ellipsoid. The contemporary studies go to well known research of Rayleigh.


See also

*
Codes for electromagnetic scattering by spheres Codes for electromagnetic scattering by spheres - this article list codes for electromagnetic scattering by a homogeneous sphere, layered sphere, and cluster of spheres. Solution techniques Majority of existing codes for calculation of electromagn ...
* Computational electromagnetics *
Light scattering by particles Light scattering by particles is the process by which small particles (e.g. ice crystals, dust, atmospheric particulates, cosmic dust, and blood cells) light scattering, scatter light causing optical phenomena such as the Rayleigh scattering, blue ...
* List of atmospheric radiative transfer codes *
Optical properties of water and ice The refractive index of properties of water, water at 20 °C for visible light is 1.33. The refractive index of normal ice is 1.31 (from List of refractive indices). In general, an index of refraction is a complex number with real and imagina ...


References


Further reading

* * * * * *


External links


SCATTERLIB
an
scattport.org
are collections of light scattering codes with implementations of Mie solutions in Fortran, C++, IDL, Pascal,
Mathematica Wolfram (previously known as Mathematica and Wolfram Mathematica) is a software system with built-in libraries for several areas of technical computing that allows machine learning, statistics, symbolic computation, data manipulation, network ...
, and Mathcad
JMIE
(2D C++ code to calculate the analytical fields around an infinite cylinder, developed by Jeffrey M. McMahon)
ScatLab
Mie scattering software for Windows.
STRATIFY
MATLAB MATLAB (an abbreviation of "MATrix LABoratory") is a proprietary multi-paradigm programming language and numeric computing environment developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementat ...
code of scattering from multilayered spheres in cases where the source is a point dipole and a plane wave. Description i
arXiv:2006.06512

Scattnlay
an open-source C++ Mie solution package with Python and
JavaScript JavaScript (), often abbreviated as JS, is a programming language and core technology of the World Wide Web, alongside HTML and CSS. Ninety-nine percent of websites use JavaScript on the client side for webpage behavior. Web browsers have ...
wrappers. Provides far-field and near-field simulation results for multilayered spheres.
Online Mie scattering calculator
provides simulation of scattering properties (including multipole decomposition) and near-field maps for bulk, core-shell, and multilayer spheres. Material parameters include all nk-data files fro
refractiveindex.info
website. The source code is part o
Scattnlay
project.
Online Mie solution calculator
is available, with documentation in German and English.

produces beautiful graphs over a range of parameters.
phpMie
Online Mie scattering calculator written on PHP.
Mie resonance
mediated light diffusion and random lasing.
Mie solution for spherical particles

PyMieScatt
a Mie solution package written in Python.
pyMieForAll
an open-source C++ Mie solution package with Python wrapper. {{DEFAULTSORT:Mie Theory Radio frequency propagation Scattering, absorption and radiative transfer (optics) Visibility