The wavelength-dependent complex refractive index of hygroscopic aerosol particles and other aqueous media: an effective oscillator model

Using cavity-enhanced Raman spectroscopy of single, optically trapped droplets, we measure both the real and imaginary parts of the refractive index of NaCl, NaNO3,  (NH4)2SO4, MgSO4, citric acid and a 1:1 molar ratio NaCl:NaNO3 aqueous solutions at a range of water activities.