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Determination of the optical constants of polydisperse particulate systems in the UV-Vis-NIR region

Lookup NU author(s): Maria Velazco-Roa, Dr Suresh Thennadil


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A method to extract the optical constants n(λ) and k(λ) of spherical particles from a polydisperse (broad and/or multimodal) suspension at concentrations where multiple light scattering effects are significant, is presented. The optical constants are estimated from total diffuse reflectance and transmittance measurements using a single integrating sphere method and inverting the measurements using the Radiative Transfer Equation (RTE) and the Mie theory for scattering by polydisperse spherical particles. The Adding Doubling method is used to solve the RTE. The method is tested by applying it to three different polydisperse polystyrene suspensions and extracting the optical constants of polystyrene particles in the wavelength range of 450 - 1200nm. The effect of polydispersity on the estimated values of the optical constants is also discussed. A comparison of n(λ) and k(λ) obtained using the exact Mie and the approximate Henyey-Greenstein (HG) phase functions was done to evaluate the error in the estimated values due to the use of the HG approximation.

Publication metadata

Author(s): Velazco Roa MA, Thennadil SN

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: AIChE Annual Meeting: 5th World Congress on Particle Technology

Year of Conference: 2006

Pages: 8pp