Hannover 2010 – wissenschaftliches Programm
Q 9.5: Vortrag
Montag, 8. März 2010, 17:45–18:00, A 320
Antiblockade of Rydberg excitation in an ultracold gas — •Christoph S. Hofmann1, Thomas Amthor1, Christian Giese2, Georg Günter1, Hanna Schempp1, Nele Müller1, and Matthias Weidemüller1 — 1Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg — 2Physikalisches Institut, Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg
The long-range character of strong Rydberg–Rydberg interactions gives rise to phenomena such as the interaction-induced blockade of Rydberg excitation. The opposite effect, the so-called antiblockade of excitation has recently been proposed for a three-level two-photon Rydberg excitation scheme, in which an Autler-Townes splitting is induced by strong coupling laser at the lower transition . When the coupling energy matches the interaction energy of the long-range Rydberg interactions, the otherwise blocked excitation of close pairs becomes possible. We present the first experimental observation of the antiblockade in an ultracold Rydberg gas . To reveal this effect we use time-resolved ionization detection. In this way we monitor the distribution of excited-pair distances, which allows us to clearly observe additional excitation (antiblockade) of pairs at small distances out of a random arrangement of atoms. A model based on a pair interaction Hamiltonian is presented which nicely reproduces our experimental observations and allows to analyze the distribution of nearest neighbor distances.
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 T. Amthor et al., arXiv:0909.0837v1