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Molécules froides: formation, piégeage et spectroscopie. -Accumulation de dimères de césium dans un piège quadrupolaire magnétique. -Spectroscopie par frustration de photoassociation.

Abstract : This thesis deals with the study of cold molecules obtained through the cold atom photoassociation technique. Our study is focused both on manipulating external degrees of freedom of these Cs2 molecules and on studying their internal interactions.

A quadrupolar magnetic trap of about 2.10^5 cold Cs2 molecules is demonstrated. The trap lifetime is on the order of 600ms, mainly limited by the background gas pressure. The trapped molecules are identified, which allows the determination of the trapped molecule cloud temperature, which is about 35uK. A dipolar trap is set up bythe use of a focused CO2 laser beam.

Moreover, this thesis desbribes a two-photon photoassociation spectroscopy. We report the first study of two-photon photoassociation line shapes, which exhibit typical Fano profiles.
Taking advantage of the detailed understanding of these line shapes, we measure over one hundred high-lying level energies with an accuracy on the order of 10MHz. Then we interpret theoretically these energies. The huge hyperfine structure of the Cesium atom binds us to solve a coupled channel Schrödinger equation for internuclear distances above 15a0. Hence we use an asymptotic theory to fit the potential parameters of the Cs2 dimer. We adjust those parameters by the mean of both evolutionnary strategies and deterministic optimum seeking. This is followed by a careful statistics study, which leads to a very accurate determination of the Vander Waals coefficient. Moreover we report the first experimental determination of the exchange interaction amplitude.
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Contributor : Nicolas Vanhaecke <>
Submitted on : Friday, January 23, 2004 - 6:19:15 PM
Last modification on : Wednesday, September 16, 2020 - 4:04:43 PM
Long-term archiving on: : Friday, April 2, 2010 - 7:39:53 PM

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Nicolas Vanhaecke. Molécules froides: formation, piégeage et spectroscopie. -Accumulation de dimères de césium dans un piège quadrupolaire magnétique. -Spectroscopie par frustration de photoassociation.. Physique Atomique [physics.atom-ph]. Ecole Polytechnique X, 2003. Français. ⟨tel-00004296⟩

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