Retarded long-range potentials for the alkali-metal atoms and a   perfectly conducting wall
  The retarded long-range potentials for hydrogen and alkali-metal atoms in their ground states and a perfectly conducting wall are calculated. The potentials are given over a wide range of atom-wall distances and the validity of the approximations used is established. 
M. Marinescu, A. Dalgarno, and J. F. Babb