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A: Atomphysik

A 6: Atomic Clusters and Cold Atoms I

A 6.4: Invited Talk

Saturday, March 5, 2005, 12:00–12:30, HU 3075

Ultralong-range interactions in a frozen Rydberg gas — •Markus Reetz-Lamour, Thomas Amthor, Johannes Deiglmayr, Kilian Singer, and Matthias Weidemüller — Physikalisches Institut der Universität Freiburg, 79104 Freiburg, Germany

We review our recent experiments on interaction-induced effects in a gas of ultracold Rydberg atoms excited from a laser-cooled rubidium cloud [1]. The van-der-Waals interaction between a pair of Rydberg atoms separated as far as 100,000 Bohr radii features two important effects: spectral broadening of the resonance lines and suppression of excitation with increasing Rydberg density. The line broadenings observed in high-resolution Rydberg spectroscopy are interpreted in terms of level shifts of Rydberg pairs due to their interaction. The density-dependent suppression of excitation marks the onset of an interaction-induced local blockade. Additional resonances are interpreted in terms of molecular potential crossovers.

[1] Singer et al., Phys. Rev. Lett. 93, 163001 (2004); Singer et al., J. Phys. B, in press (2004).