Mie scattering from strongly absorbing airborne particles in a photophoretic trap

High-precision light scattering measurements of single, absorbing aerosol particles pose a challenge as the strong attenuation of light results in featureless spectra. Using the Kramers-Kronig relations and broadband light scattering, we develop and implement a method for the retrieval of both the size and the complex refractive index of particles that are strongly absorbing across large spectral regions. This method is validated using both synthetic spectra and scattered light intensity measurements from single dye-doped polystyrene beads of known radii that are held using a photophoretic trap.