High-level ab initio calculations have been performed on the Hg + · Rg and Cd + · Rg species, where Rgv Heu Rn. Potential-energy curves have been calculated over a wide range of internuclear separation, sampling the repulsive, equilibrium, and long-range regions. From these curves, rovibrational and spectroscopic constants were derived and compared to those available from previous studies. In addition, transport coefficients were calculated and compared to the available experimental data for the cases of Hg + in He, Ne, and Ar. There are two interesting features relating to the mobility results. One is the development of a "mobility minimum" for Hg + in the heavier rare gases-with weaker minima being found for Cd + ; a "rule of thumb" is presented for determining when mobility minima might appear. The second is that excellent agreement is found for the direct calculation of mobilities for Hg + in 22 Ne, and those obtained by scaling the 20 Ne mobilities. The latter result allows us to conclude that the mobilities of the various combinations of isotopes can be calculated from the results herein via a mass scaling.

High-level ab initio CCSD(T) calculations are performed in order to obtain accurate interaction potentials for the Br(-) anion interacting with each rare gas (Rg) atom. For the Rg atoms from He to Ar, two approaches are taken. The first one implements a relativistic core potential and an aug-cc-pVQZ basis set for bromine, an aug-cc-pV5Z basis set for Rg, and a set of bond functions placed at the midpoint of the Rg-Br distance. The second one uses the all-electron approximation with aug-cc-pV5Z bases further augmented by an extra diffuse function in each shell. Comparison reveals close similarity between both sets of results, so for Rg atoms from Kr to Rn only the second approach is exploited. Calculated potentials are assessed against the previous empirical, semiempirical, and ab initio potentials, and against available beam scattering data, zero electron kinetic energy spectroscopic data, and various sets of the measured ion mobilities and diffusion coefficients. This multiproperty analysis leads to the conclusion that the present potentials are consistently good for the whole series of Br(-)-Rg pairs over the whole range of internuclear distances covered.