Ultraviolet broadband light scattering for optically-trapped submicron-sized aerosol particles

Gregory David, Kivanc Esat, Irina Ritsch and Ruth Signorell

We describe a broadband light scattering setup for the characterization of size and refractive index of single submicron-to-micron sized aerosol particles. Individual particles are isolated in air by a quadruple Bessel beam optical trap or a counter-propagating optical tweezer. The use of very broadband radiation in the wavelength range from 320 to 700 nm covering the ultraviolet region allows to size submicron particles. We show that a broad wavelength range is required to determine the particle radius and the refractive index with an uncertainty of several nanometers and ~ 0.01, respectively. The smallest particle radius that can be accurately determined lies around 300 nm. Wavelength-dependent refractive index data over a broad range are obtained, including the ultraviolet region where corresponding data are rare. Four different applications are discussed: 1) the sizing of submicron PSL spheres, 2) the evaporation of binary glycerol water droplets, 3) hydration/dehydration cycling of aqueous potassium carbonate droplets, and 4) photochemical reactions of oleic acid droplets.

DOI