EGAS41 - Swansea University

41 st EGAS CP 167 Gdańsk 2009
Ultra-cold Rydberg atoms in magneto-optic and optical dipole
traps
M.J. Piotrowicz ∗ , C. MacCormick, A. Kowalczyk, S. Bergamini
Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes,
MK7 6AA, UK
∗ Corresponding author: m.piotrowicz@open.ac.uk,
In a Rydberg atom an electron is excited to a state with high principal quantum number
n, very close to the ionisation threshold. Having so weakly bound electron, these atoms
exhibit extreme sensitivity to external fields, including fields due to nearby Rydberg
atoms. One excited atom can inhibit the excitation of its neighbours thus causing a
“local blockade effect”. This leads to the formation of spatial regions in which only a
small fraction of the atoms can be excited. The dynamics of a dense sample of ultracold
Rydberg gas, prepared by exciting laser-cooled alkali atoms, are dominated by these
enhanced interactions to the extent that the atomic motion is unimportant. At the Open
University, we are developing an experiment to study small numbers of atoms stored in
micron sized optical dipole traps, in which the strong Rydberg-Rydberg interactions give
rise to collective states of the entire sample.
In our experiment, 87 Rb atoms are trapped and cooled in a magneto-optic trap and
then transferred to an optical dipole trap where they then undergo a two-photon laser
excitation to a Rydberg state. Our objective is to study the collective states in a wide
range of situations by controlling the density, Rydberg state or applied external fields.
The current status of the experiment will be described.
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