The Onsager reaction field as a screened self-interaction in refractive index theory

The authors give a microscopic derivation of a formula of Bottcher's type for the refractive index. In this a macroscopic cavity field replaces the Lorentz internal field and the polarizability is modified by many-body self-interactions. These combine both an Onsager type reaction field and a screened radiation reaction. The microscopic argument resolves apparent conflict between the two different macroscopic approaches to the internal field problem.