Experimental and Theoretical Studies of Light Scattering from Irregularly Shaped Particles

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The goal of this project is to develop a complete, comprehensive and quantitative description of light scattering by irregularly shaped particles. A device for simultaneous multi-angle, calibrated scattering matrix measurements over essentially all angles from 0.1 degrees to 180 degrees will be designed and built. An important characteristic of the device, not found in previous studies of irregularly shaped particles, is the ability to go to very small angles necessary to detect the Guinier and Rayleigh scattering regimes. With this device, scattering by a wide variety of irregular particles including soot aggregates, humidified soot aggregates and then dried soot aggregates, mineral dusts and humidified dusts, and crystalline solids with geometric shapes will be studied. Such particles are of significance for atmospheric aerosols and the global environment. The combined experimental and theoretical work will yield a quantitative yet physical description of scattering by all types of particles. This description will be both accurate and straightforward to implement into global climate models.Intellectual Merit: The study will apply and test broadly the q-space analysis method to both the experimental data and systematic theoretical calculations. The method is a completely new way of analyzing light scattering that past work indicates will be broadly applicable. With this q-space perspective, the systematic studies should yield a new physical picture of scattering that will give an unprecedented intellectual intuition on how scattering works.Broader Impacts: One of the most significant problems facing humanity today is global climate change. The results of this research will have direct bearing on the problem of how aerosols affect our global environment. The goal of this study is to understand and accurately describe light scattering from any kind of particle including the wide variety of non-spherical shapes that occur in the atmosphere. With such knowledge, the direct impact of aerosols on the environment can be predicted and the aerosol content in the atmosphere can be accurately detected and measured.There are a number of projects regarding education, outreach and curriculum development that will directly result from or be significantly related to this work including: a summer workshop for teen women, involvement of undergraduates in research, an upper level undergraduate course on light scattering, talks at high schools, mentorship of graduate students, and writing of a monograph on light scattering.