10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Scattering Matrices of Single Levitated Particles
ALEXANDRIA JOHNSON, Maria Zawadowicz, Sara Lance, Daniel Cziczo, MIT
Abstract Number: 1617 Working Group: Instrumentation
Abstract Suspended particulates are a ubiquitous feature of planetary atmospheres. However, major gaps remain in our understanding of how non-spherical particles scatter and polarize incident radiation. Modeling the highly complex scattering phase functions produced by non-spherical particles is challenging and broad stroke simplification of particulate properties, such as with an oblate spheroid approximation, can lead to large uncertainties in numerical model outputs and satellite retrieval corrections.
With this in mind we aim to directly measure how non-spherical atmospheric particulates interact with radiation through the development of a single particle scatterometer. Our novel instrument consists of a vapor diffusion electrodynamic balance (EDB), used to levitate single particles in a precisely controlled atmospheric environment, coupled with a photomultiplier for the collection of a scattering phase function, or scattered light as a function of angle along the plane of illumination.
Here we will discuss the development of our EDB scatterometer, validation experiments with spherical particles, and preliminary results on non-spherical particles. For spherical validation experiments our results will be compared directly to Mie theory and used to address any biases in our measurements. Although single particle studies allow for the precise control of a sample and its environment, their relevance to atmospheres and the complexity therein can be questioned. To address this we will discuss the relationship between single particle and bulk sample (or particle ensemble) non-spherical scattering phase functions through comparison with data from the Amsterdam-Granada Light Scattering Database.
Future work will be done towards expanding the system to include the collection of polarized light, with the ultimate goal of retrieving Muller matrix elements for a full description of scattering on the single particle basis. We also aim to expand the temperature regime of the EDB beyond that of Earth for atmospheric studies relevant to other solar system bodies and ‘cooler’ exoplanets.