Extinction, scattering, and absorption efficiency factors for a concentric sphere of a nonlight absorbing nucleus (m = 1.5) and an absorbing shell (m = 1.95 - 0.66i) were calculated based on the theory of Aden and Kerker. For small size parameters (v < 1), the magnitude of the extinction efficiency factor is markedly affected by the shell thickness. An approximating equation, based on the Rayleigh light scattering equation, is presented which relates the increase of the extinction efficiency factor of an absorbing sphere over the extinction efficiency factor of a nonabsorbing sphere to the pertinent variables (refractive index and size parameter).
Michael J. Pilat, "Optical Efficiency Factors for Concentric Spheres," Appl. Opt. 6, 1555-1558 (1967)