Comparison of Measured and Theoretical Scattering and Polarization Properties of Narrow Size Range Irregular Sediment Particles

The predominant use of theoretical models for angular light scattering due to particles is largely due to limited number of actual measurements. Measuring the angular scattering is difficult due to the wide dynamic range of intensity as a function of angle, as well as variability across particle types and environments. The present work continues ongoing research by the authors related to the scattering properties of irregular particles. Using the recently developed LISST-VSF instrument, we measured the VSF at angles from approximately 0.1 to 150 degrees, as well as the degree of linear polarization from 15 to 150 degrees, of narrow size distributions of irregular silt and sand-sized particles (Arizona Test Dust) in the laboratory. The general trend in these observations is as expected: larger particles become more strongly peaked in the near-forward angles., The measured phase functions also had greatly enhanced scattering in the mid angles, approximately 40 to 100 degrees, compared with the Petzold phase functions. Measured degree of linear polarization was significantly different from theoretical predictions, likely due to particle shape and composition.