A Rydberg and a ground-state atom can form ultralong range diatomic molecules provided the interaction between the ground-state atom and the Rydberg electron is attractive [C. H. Greene, et al., Phys. Rev. Lett. 85, 2458 (2000)]. A repulsive interact
ion does not support bound states. However, as we will show, adding a second ground-state atom, a bound triatomic molecule becomes possible constituting a Borromean Rydberg system.
