Determination of refractive index for absorbing spheres

Complex refractive index for submicron absorbing spheres was determined by simultaneously measuring absorption coefficients and number concentrations with a multiangle absorption photometer and a condensation particle counter, respectively. The absorption cross section calculated from the absorption coefficient and the number concentration was fitted to the absorption cross section calculated using Mie theory. For homogeneously dyed spheres, the absorption cross section depended on the size of sphere. For non-homogeneously dyed spheres, however, the absorption cross section had nothing to do with the size of sphere. It is concluded that the ability to measure refractive index by our method held good as long as the absorption phenomenon takes place in the near field surrounding particles surface. To the best of our knowledge, it is for the first time that the refractive index was determined by only absorption measurements and theory. This method is believed to help understand the fundamental of the optical properties for other absorbing particles. (C) 2013 Elsevier GmbH. All rights reserved.