High-level ab initio calculations are used to obtain accurate potential energy curves for Na+.Kr, Na+.Xe, and Na+.Rn. These data are used to calculate spectroscopic parameters for these three species, and the data for the whole Na+.Rg series (Rg=He-Rn) are compared. Potentials for the whole series are then used to calculate both mobilities and diffusion coefficients for Na+ moving through a bath of each of the six rare gases, under conditions that match previous experimental determinations. Different available potentials and experimental data are then statistically compared. It is concluded that the present potentials are very accurate. The potential and other data for Na+.Rn appear to be the first such reported. (C) 2003 American Institute of Physics.