title: Mechanical effect of van der waals interactions observed in real time in an ultracold Rydberg gas.
abstract: We present time-resolved spectroscopic measurements of Rydberg-Rydberg interactions between two Rydberg atoms in an ultracold gas, revealing the pair dynamics induced by long-range van der Waals interactions between the atoms. By detuning the excitation laser, a specific pair distribution is prepared. Penning ionization on a microsecond time scale serves as a probe for the pair dynamics under the influence of the attractive long-range forces. Comparison with a Monte Carlo model not only explains all spectroscopic features but also gives quantitative information about the interaction potentials. The results imply that the interaction-induced ionization rate can be influenced by the excitation laser. Surprisingly, interaction-induced ionization is also observed for Rydberg states with purely repulsive interactions.
authors.affiliation: Physikalisches Institut, Universität Freiburg, Freiburg, Germany. thomas.amthor@physik.uni-freiburg.de
authors.forename: T
authors.initials: T
authors.lastname: Amthor
authors.forename: M
authors.initials: M
authors.lastname: Reetz-Lamour
authors.forename: S
authors.initials: S
authors.lastname: Westermann
authors.forename: J
authors.initials: J
authors.lastname: Denskat
authors.forename: M
authors.initials: M
authors.lastname: Weidemüller