A Casimir approach for radiative self-energy
  We apply a Casimir energy approach to evaluate the self-energy or one-photon radiative correction for an electron in a hydrogen orbital. This linking of the Lamb shift to the Casimir effect is obtained by treating the hydrogen orbital as a one-electron shell and including the probability of the electron being at a particular radius in that orbital and the probability that the electron will interact with a virtual photon of a given energy. 
Allan Rosencwaig