Long-range interactions of sodium atoms

Long-range interaction potentials between two and three sodium atoms, between a sodium atom and a perfectly conducting wall, and for a sodium atom between two perfectly conducting walls, are calculated with an electric-dipole oscillator strength distribution constructed from combinations of experimental and theoretical energy levels, oscillator strengths, and photoionization cross section data, constrained by accurate values of oscillator strength sum rules. The leading dispersion coefficients for Na-Na and Na-Na-Na and the Lennard-Jones coefficient for the Na-wall system are determined. For Na-Na and for the Na-wall systems, the retarded (Casimir) potentials are also calculated.