Light scattering from spherical and irregular particles over a wide angular range

Abstract

We present laboratory measurements of angular light scattering intensity for aerosolized, micron-sized, irregularly shaped aluminum oxide (Al2O3) abrasive powders with different grit sizes. The measurements were carried out with the scattering angle ranging from 0.32° to 177.6°. First, we demonstrate that the light scattering inferred diameters were in good agreement with the intensity-weighted mean sizes and discuss the importance of intensity-weighted size distributions. Second, the wide range of scattering angles motivated us to visualize the same scattering intensity data with three methods: (a) logarithmically versus linear scattering angle θ, (b) logarithmically versus the logarithmic magnitude of the scattering wave vector q for forward scattering, the method of Q − space analysis, and (c) logarithmically (last ≈ 20 degrees of θ) versus linear phase angle (180° - θ). The combination of these viewpoints yields a comprehensive description of the scattering that corresponds to dividing angular scattering into three regimes: forward−, side–, and back − scattering. The light scattering measurements were compared to the Mie scattering calculated for homogenous, spherical particles with the same volume-equivalent size distribution as that of the Al2O3 particles determined with an aerodynamic particle sizer. Experimental and Mie-theory results were well-matched in the forward regime which is clearly shown in Q − space but showed a poor matching in the side and backscattering regimes, as displayed in θ− and (180°- θ) space, respectively.