Light scattering from spherical and irregular particles over a wide angular range
Prakash Gautam, Hans Moosmüller, Justin B. Maughan, C. M. Sorensen
Abstract
We present laboratory measurements of angular light scattering intensity for aerosolized, micron-sized, irregularly shaped aluminum oxide (Al 2 O 3 ) 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 intensityweighted 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 h, (b) logarithmically versus the logarithmic magnitude of the scattering wave vector q for forward scattering, the method of Qspace analysis, and (c) logarithmically (last 20 degrees of h) versus linear phase angle (180 h). The combination of these viewpoints yields a comprehensive description of the scattering that corresponds to dividing angular scattering into three regimes: forward-, side-, and backscattering. 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 Al 2 O 3 particles determined with an aerodynamic particle sizer. Experimental and Mie-theory results were well-matched in the forward regime which is clearly shown in Qspace but showed a poor matching in the side and backscattering regimes, as displayed in h-and (180 h) space, respectively.