Formation and properties of Rydberg macrodimers

We investigate the interaction between two rubidium atoms in highly excited Rydberg states, and find that very long-range potential wells exist. These wells are shown to support many bound states. We calculate the properties of the wells and bound levels, and show that their lifetimes are limited by that of the constituent Rydberg atoms. We also show how these micrometer-sized bound states can be populated via photoassociation (PA), and how the signature of the admixing of various l characters producing the potential wells could be probed. We discuss sharp variations of the PA rate, which could act as a switching mechanism with potential application to quantum information processing.