• atomic optics
• cold rydberg atoms

Rydberg atoms (the atoms in excited states with principal quantum number n>20) have very large polarizability (which
scales as n^2) and therefore
interactions among them (van der Waals) are strong, on the order of about 10MHz for the typical mean interparticle distance of laser-cooled atomic gases (order of micrometer).


For this reason, and because of the great control their enhanced properties offer,
they have been proposed as simulators of many-body physics.

The excitation dynamics through laser light to the Rydberg state in a cold cloud (about 100microkelvin) of Rb atoms
has already shown evidences of strong
correlations which are a direct consequence of the interactions.

Here we present an experimental procedure which yields information on the interactions not through
the excitation dynamics, but rather through the dynamics of de-excitation:
we add, after the excitation process, a de-excitation phase through a coupling with a
rapidly-decaying level and measure the number of remaining excitations as
a function of time and of the frequency of the de-excitation laser.

A part of the thesis is dedicated to the experimental technique needed for the de-excitation process,
which requires a rapid change of the frequency of one of the excitation lasers.
We also briefly discuss other techniques involving time-varying frequencies (periodic modulation and sweep)
and their application to studies of Rydberg excitation dynamics.

The main chapter of this thesis is devoted to the results of the exploration of the de-excitation
scheme. We interpret our results in the light of numerical simulations which demonstrate that both the dynamics and the frequency dependence of the de-excitation yield information
about the spatial arrangement of the initial Rydberg excitations. We conclude by suggesting possible applications of our
procedure, such as the controlled preparation of spatial arrangements of Rydberg excitations by selectively removing a class of atoms at a certain interaction energy.