  We propose a novel scheme to normalize scattering modes of the
electromagnetic field. By relying on analytical solutions for Maxwell's
equations in the homogenous medium outside the scatterer, we derive
normalization conditions that only depend on the electromagnetic field on the
surface of a sphere containing the scatterer. We pay special attention to the
important cases of plane wave illumination and illumination with a multipolar
field, for which an explicit and easy to use normalization condition is
derived. We demonstrate the versatility of our method by normalizing scattering
modes of some selected metallic and dielectric scatterers of different
geometries in the context of different application scenarios. Since every
quantum mechanical treatment of light-matter interaction requires the proper
normalization of electromagnetic fields, we deem our proposed normalization
scheme broadly applicable independent of the scatterer involved.
