The range of validity of the anomalous diffraction approximation to electromagnetic scattering by a sphere.
The ranges of refractive index and particle size over which the anomalous diffraction approximation is valid to within 15%, 50%O, and 100% are mapped. The approximation is found to have a broader range of applicability for the extinction efficiency than the Rayleigh-Gans approximation. The large range of validity explains the success of schemes for determining particle size distributions of spheres from extinction measurements based on analytic inversions of formulas containing the approximation.
Anomalous diffraction of light with geometrical path statistics of rays and a Gaussian ray approximation.
The anomalous-diffraction theory (ADT) of extinction of light by soft particles is shown to be determined by a statistical distribution of the geometrical paths of individual rays inside the particles. Light extinction depends on the mean and the mean-squared geometrical paths of the rays. Analytical formulas for optical efficiencies from a Gaussian distribution of the geometrical paths of rays are derived. This Gaussian ray approximation reduces to the exact ADT in the intermediate case of light scattering for an arbitrary soft particle and describes well the extinction of light from a system of randomly oriented and (or) polydisperse particles. The implications for probing of the sizes and shapes of particles by light extinction are discussed.
Determination of particle size by the minima and maxima in the angular dependence of the scattered light. Range of validity of the method
Abstract The range of validity of the method of determining particle size by the angular location of the minima and maxima in light scattering intensity is explored, and the results are presented in the form of 2% and 10% error contour charts. The method is valid over a greater region of the m - α domain than is the Rayleigh-Gans theory for intensity functions.