| Ultralong range Rydberg molecules have been observed by photoassociation spectroscopy recently in cold Rb atomic gases. These weakly bound molecules are formed by low energy scattering of Rydberg electron with ground state atoms, with binding length up to several thousand Bohr for high Rydberg states. A Green's function calculation gives consistent potential curves and is shown to explain most of the observed dimer lines. We reveal a new binding mechanism based on quantum reflection at a shape resonance for electron-atom scattering. |
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