23 December 1994 Optical properties of core-mantle spheroidal particles
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The new solution of the problem of light scattering by coated spheroids was used to calculate the optical properties of prolate and oblate particles. The solution was obtained by the method of separation of variables for confocal spheroids. We consider the silicate core ice mantle particles and present the extinction cross-sections for prolate and oblate spheroids with the refractive indices mcore equals 1.7 + Oi, 1.7 + 0.1i and mmantle equals 1.3, the aspect ratio (a/b)mantle equals 2 and various volume ratios Vcore/Vtotal. The results are plotted for different size parameters xv equals 2(pi) rv/(lambda) , where rv is the radius of equivolume sphere and (lambda) is the wavelength of incident radiation. The main conclusions are: (a) if Vcore/Vtotal equals 0.5, the optical properties of a core-mantle particle are determined mainly by its core: for prolate non-absorbing spheroids when xv <EQ 4.5; for prolate absorbing spheroids when xv <EQ 4.5 or xv > 10, for oblate absorbing and non-absorbing spheroids when xv <EQ 10. (b) the linear growth of the extinction cross-sections on the volume ratio Vcore/Vtotal is obtained for prolate particles with xv equals 1 and 2. (c) the non-linear increase of cross- sections is obtained for oblate particles with size parameters xv equals 1 - 5. (d) the small imaginary part of the core refractive index m [Im(m) < 0.01] practically does not change the optical properties of an inhomogeneous particle. When the imaginary part reaches 0.1, the noticeable changes of cross-sections may be detected.
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Vadim V. Somsikov, Vadim V. Somsikov, Victor G. Farafonov, Victor G. Farafonov, } "Optical properties of core-mantle spheroidal particles", Proc. SPIE 2309, Passive Infrared Remote Sensing of Clouds and the Atmosphere II, (23 December 1994); doi: 10.1117/12.196666; https://doi.org/10.1117/12.196666

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