Resonance Scattering from Absorbing Spheres

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Abstract
Electromagnetic scattering from absorbing spheres near resonances is illustrated through calculations of the dependence of the efficiency factor for extinction Qext and of the angular scattering functions on n1 and n2 (the real and imaginary parts of the index of refraction). Among the interesting features discussed are the following: (1) the maximum value of Qext at the first resonance decreases rapidly when a small amount of absorption is introduced; (2) over a considerable range of the parameters the width of the first resonance of Qext is proportional to n1−4 when there is no absorption and to n2n1−2 when there is absorption; (3) when n1 ≫ 1, the scattered intensity near the first resonance is predominately forward, symmetrical, or predominately backward when x is respectively somewhat smaller than, equal to, or larger than the resonance value; (4) as n2 increases, the forward scattered intensity first increases before it decreases, when x ≥ 1 and for most values of n1; (5) strong forward scattering occurs on one side of a resonance and strong backward scattering on the other side, although this effect may be obscured by other factors for high multipole resonances.