“…Although the method given in [7] is also applicable for dielectric spheroids, from our previous experience on scattering problems by spheroids [7], [9], it is more convenient to construct our closed-form solution by expressing the fields in terms of spherical eigenvectors and use a shape perturbation method, rather than expressing them in terms of spheroidal eigenvectors and applying asymptotic techniques. The reason for this is that, if one employs the method in [7], then he has to deal with the asymptotic properties, not only of the spheroidal wave functions, but also of the related eigenvalues, of the normalization constants, and of the cumbersome inner products relating integrals of the angular spheroidal functions. On the other hand, the shape perturbation method relies only on the asymptotic expansions of the spherical eigenvectors in terms of the standard spherical Bessel functions.…”