Application

The application of the Mie theory for the evaluation of laser diffraction measurements is appropriate for spherical particles of pure materials with the following properties:

opaque particles	expected size distribution:  90% below 2?m
transparent particles	expected size distribution:  90% below 200?m

The application of Mie theory is not suited for non-spherical particles, for mixtures of various materials, and for particles with unknown refractive index.

Technical Specifications

sensors:	Laser Diffraction Sensors	HELOS or MYTOS
measuring ranges:	R1 to R4	particle size < 350?m
range of complex refractive index n - i*k:	refraction coefficient 0.01 <= n <= 3.0	absorption coefficient 0.0 <= k <= 5.0
evaluation:	HRLD evaluation mode	high resolution, high speed

Background Information

The basis for applying the Mie theory is the publication by G. Mie[2] in 1908, in which an exact solution of Maxwell's equations was formulated for scattering of electromagnetic waves by spherical particles. This solution is known as the Mie theory. A detailed description is presented in [3].

For the application of Mie theory, the complex index of refraction, m, must be known. It is defined as

m = n - i * k

where
n         the refractive index, describes reflection and refraction, and
k         the absorption coefficient, describes the absorption
i         the unit of the imaginary fraction of m.