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.
Aerosol studies by light scattering. I. Particle size distribution by polarization ratio method
Abstract A method for determination of particle size distribution of spherical particles in the submicron range from the polarization ratio of the scattered light is described. A logarithmic distribution is assumed. Experimental values of the polarization ratio are compared with theoretical values at 19 angles. Theoretical computations have been carried out for refractive indices, m = 1.43, 1.51, and 2.074, for modal values of the size parameters α = 1.9(.1)15.0 , for logarithmic standard deviations, σ = .005(.005)−.155; .16(.01).30, and for angles of observation, θ = 30°(5°)130°.
Maximum particle sizes in polydispersed aerosols
Abstract The size distributions of mercury and sulfur aerosols have been investigated by a light scattering—settling technique and the results compared with direct electron microscope observations. For the larger size aerosols the maximum size obtained by light scattering agrees with the electron microscope maximum but the distribution curves differ. For smaller aerosols (maximum by electron microscope less than 0.1 μ) the light scattering shows no maximum size. These discrepancies are attributed to convection and coagulation. The liquid nature of sulfur aerosols is demonstrated by photomicrography and a new technique of preparing them for the electron microscope is described.