Multipole radiation in an inhomogeneous dispersive medium with spherical symmetry

The multipole field expansion in an inhomogeneous dispersive medium with spherically symmetric dielectric constant is discussed. Unlike the case of a homogeneous medium, the radial functions corresponding to electric multipole Field and magnetic multipole field will now be determined separately by their own equations and boundary relations. Some emphasis is put on electric dipole radiation to give the enhancement factor of the Einstein A coefficient.