Abstract
Van der Waals interactions between the valence electrons of the barium atom and the closed-shell cores have been studied using ab initio methods with a combination of pseudopotentials and core polarisation potential. We have reported the potential energy curves, the spectroscopic constants, the vibrational levels as well as the electric dipole moments for the ground and several excited states of Ba
+
Kr and BaKr complexes. Interesting behaviour has been observed in the potential energy curves, particularly for Σ
+
states. This can show the strong repulsive interactions between Rydberg electrons and the Krypton atom.