Separation-Dependent Near-Field Effects in Mie Scattering Spectra of Two Optically Trapped Aerosol Droplets

The backscattering of ultraviolet and visible light by a model organic aerosol droplet, squalane, is investigated upon approach of a second isolated droplet at varying separations Illumination and collection of light is along the interparticle axis. The conditions replicate typical broadband light spectroscopy studies of atmospheric aerosol. -Matrix near-field modelling, which includes near-field effects, predicts separation-dependent changes in the intensity of the backscattered light on close approach of neighbouring spheres. However, the experimental results show no evidence of separation-dependent near-field effects on the scattering. The results are
best replicated by modelling the droplets as individual scatterers.