Long-range interactions between rubidium and potassium Rydberg atoms

We investigate the long-range, two-body interactions between rubidium and potassium atoms in highly excited (n = 70) Rydberg states. After establishing properly symmetrized asymptotic basis states, we diagonalize an interaction Hamiltonian consisting of the standard Coulombic potential expansion and atomic fine structure to calculate electronic potential energy curves. We find that when both atoms are excited to either the 70s state or the 70p state, both the Omega = 0(+) symmetry interactions and the Omega = 0(-) symmetry interactions demonstrate a deep potential well capable of supportingmany bound levels; the sizes of the corresponding dimer states are of the order of 2.25 mu m. We establish n-scaling relations for the equilibrium separation Re and the dissociation energy De and find these relations to be consistent with similar calculations involving the homonuclear interactions between rubidium and cesium. We discuss the specific effects of (sic) mixing and the exact composition of the calculated potential well via the expansion coefficients of the asymptotic basis states. Finally, we apply a Landau-Zener treatment to show that the dimer states are stable with respect to predissociation.