Polyatomic Molecules Formed with a Rydberg Atom in an Ultracold   Environment
  We investigate properties of ultralong-range polyatomic molecules formed with a Rb Rydberg atom and several ground-state atoms whose distance from the Rydberg atom is of the order of n^2a_0, where n is the principle quantum number of the Rydberg electron. In particular, we put emphasis on the splitting of the energy levels, and elucidate the nature of the splitting via the construction of symmetry-adapted orbitals. 
Ivan C. H. Liu and Jan M. Rost