LIGHT-SCATTERING BY A CORE-MANTLE SPHEROIDAL PARTICLE

A solution of the electromagnetic scattering problem for confocal coat ed spheroids has been obtained by the method of separation of variable s in a spheroidal coordinate system. The main features of the solution are (i) the incident, scattered, and internal radiation fields are di vided into two parts: an axisymmetric part independent of the azimutha l angle phi and a nonaxisymmetric part that with integration over ip g ives zero; the diffraction problems for each part are solved separatel y; (ii) the scalar potentials of the solution are chosen in a special way: Abraham's potentials (for the axisymmetric part) and a superposit ion of the potentials used for spheres and infinitely long cylinders ( for the nonaxisymmetric part). Such a procedure has been applied to ho mogeneous spheroids [Differential Equations 19, 1765 (1983); Astrophys . Space Sci. 204, 19, (1993)] and allows us to solve the light scatter ing problem for confocal spheroids with an arbitrary refractive index, size, and shape of the core or mantle. Numerical tests are described in detail. The efficiency factors have been calculated for prolate and oblate spheroids with refractive indices of 1.5 +/- 0.0i, 1.5 + 0.05i for the core and refractive indices of 1.3 + 0.0i, 1.3 + 0.05i for th e mantle. The effects of the core size and particle shape as well as t hose of absorption in the core or mantle are examined. It is found tha t the efficiency factors of the coated and homogeneous spheroids with the volume-averaged refractive index are similar to first maximum.