A single Rydberg atom inside a Bose-Einstein Condensate
Dr. Robert Löw (5. Physikalisches Institut der Universität Stuttgart)

The excitation blockade mechanism between interacting Rydberg atoms allows one to place a single Rydberg atom inside a Bose-Einstein condensate. This works even in a situation when the size of the Rydberg atom is much larger than the distance between the ground state atoms in the BEC. As a consequence of this many atoms reside inside the orbit of the wave-function of the Rydberg electron. It has been a surprise that the collisions between the Rydberg electron and the ground state atoms do not directly lead to an ionization process or some other immediate inelastic reaction. As a consequence we are able to observe a coherent interaction between many ground state atoms and a single Rydberg atom in terms of a density dependent line shift and a back-action on the shape of the BEC.
Nevertheless, after some time we do observe inelastic collisions between a neutral ground state atom and the Rydberg atom. The observed time scales, reaction channels and exothermic energy gives insight in a complex reaction dynamics. Some parts of this dynamics are understood by now and gives us a deeper insight in the pair state potentials of a Rydberg atom and a ground state atom.
In the end of the talk I will discuss how this experimental arrangement can be used to image directly the wave-function of a Rydberg atom or how it allows us to study Langevin-type dynamics in the quantum regime.