The electronic structures of the Ne2F, Ar2F, Kr2F, Xe2F, Ar2Cl, Kr2Cl, Xe2Cl, Kr2Br, Xe2Br, and Xe2I molecules have been studied on the CASSCF/CASPT2 level, with inclusion of the spin–orbit interaction. For the lowest strongly bound Rg2X(42Г) state we report RRg–Rg and RRg–X equilibrium bond lengths, dissociation energy, radiative lifetime and frequencies of three vibrational modes. Except for the antisymmetric stretch mode, a similar set of results was obtained for another five bound states above Rg2X(42Г). To compare equilibrium bond lengths and some other molecular properties, calculations were also performed for Rg2+ and RgX diatomics on the same level of theory and using the same basis sets. The ab initio results obtained in this work are of interest for experimental and theoretical studies of Rg2X(42Г) formation mechanisms.