Complex refractive index of non-spherical particles in the vis-NIR region - application to Bacillus Subtilis spores

Velazco-Roa, Maria A and Dzhongova, Elitsa and Thennadil, Suresh N. (2008) Complex refractive index of non-spherical particles in the vis-NIR region - application to Bacillus Subtilis spores. Applied Optics, 47 (33). pp. 6183-6189. ISSN 1559-128X

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Abstract

A method is presented for the estimation of optical constants in the ultraviolet-visible-near-infrared (UVVis-NIR) region of nonspherical particles in a suspension at concentrations where multiple scattering issignificant. The optical constants are obtained by an inversion technique using the adding-doubling method to solve the radiative transfer equation in combination with the single scattering theories for modelling scattering by nonspherical particles. Two methods for describing scattering by single scatteringare considered: the T-matrix method and the approximate but computationally simpler Rayleigh-Gans-Debye (RGD) approximation. The method is then applied to obtain the optical constants of Bacillussubtilis spores in the wavelength region 400-1200 nm. It is found that the optical constants obtained using the RGD approximation matches those obtained using the T-matrix method to within experimental error.