LONG-RANGE POTENTIALS, INCLUDING RETARDATION, FOR THE INTERACTION OF 2 ALKALI-METAL ATOMS

The retarded long-range potentials for the dispersion interaction arising from induced multipole moments of two ground-state alkali-metal atoms are evaluated as functions of the separation R for Li, Na, K, Rb, and Cs. Accurate atomic properties, determined using published model potentials, are utilized. Values for the potentials are given over a wide range of R. Results for H are also given. For small R the results reproduce the accepted values for the unretarded dispersion dipole-dipole (van der Waals), dipole-quadrupole, quadrupole-quadrupole, and dipole-octupole coefficients, while for R --> infinity the Casimir-Polder potentials, due to retardation or effects due to the finite speed of light, are obtained. The overlap between the retardation potentials and terms arising from the Breit-Pauli Hamiltonian is explored.