Determining the size and refractive index of single aerosol particles using angular light scattering and Mie resonances

Alison Bain, Aidan Rafferty, Thomas C. Preston

Optical trapping allows for high precision studies of many microphysical and chemical processes as it enables measurements on the single-particle level. This has been a tremendous benefit to fundamental aerosol research. In the vast majority of these experiments, trapped particles are characterized using light scattering – most often angular light scattering (phase functions) or Mie resonance spectroscopy. In this report, we compare the radii and refractive indices of best-fit found with these two light scattering methods by trapping single aerosol particles in a relative humidity-controlled cell where we can simultaneously measure both phase functions and Mie resonances, the latter of which are found using cavity-enhanced Raman scattering. Additionally, we compare best-fits found using both one- and two-dimensional phase functions. The application of Mie theory to these light scattering problems is thoroughly reviewed. Both the accuracy and uncertainty of the best-fits that these light scattering techniques produce are investigated using a model aqueous inorganic aerosol particle.

DOI