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Photoassociation d'atomes de césium froids. Formation et caractérisation d'un nuage froid de molécules diatomiques de césium.

Abstract : In a photoassociation process, two colliding cold cesium atoms absorb one photon to form an ultracold molecule, electronically excited in a well defined ro-vibration level. Because of the small initial kinetic energy of the free atoms, the photoassociation is resonant and permits high resolution spectroscopy of long-range states. We report spectra for states correlated to the excitated limit 6S+6P. The 1u (6S+6P3/2) state is a pure long-range molecules. It hardly consists in a molecule, but rather in a pair of two atoms linked at 1,5 nm by the multipolar electrostatic interaction. The intensity modulation of spectral lines for a given vibrationnal progression reflects the nodal structure of the radial s-wave function of two ground state atoms. The photoassociation of the state 0g-(6S +6P3/2) of polarized atoms permits to determine the scattering length of the triplet state of cesium (aT = -530 a0) and the Van der Waals parameter of the molecular ground state (C6 = 6510 u.a.). Photoassociation of cold cesium atoms also leads to the formation of translationnaly cold molecules in singulet and triplet fundamental states after spontaneous emission of the excitated molecules. Various schemes are characterized. The particular double-well shape of 0g-(6S+6P3/2) and 1u(6S+6P3/2) states creates a Condon point at intermediate distance. These states constitute ideal cases for very efficient formation of cold molecules. The cold molecular cloud is analyzed : temperatures as low as 20 microKelvins are measured and the distribution of the ro-vibrationnal levels is studied. The efficiencies of the photoassociation process and of the formation of cold molecules are measured, and compared with theoretical calculations.
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https://tel.archives-ouvertes.fr/tel-00600313
Contributor : Cyril Drag <>
Submitted on : Tuesday, June 14, 2011 - 3:00:25 PM
Last modification on : Wednesday, September 16, 2020 - 3:59:07 PM
Long-term archiving on: : Sunday, December 4, 2016 - 2:50:58 PM

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  • HAL Id : tel-00600313, version 1

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Cyril Drag. Photoassociation d'atomes de césium froids. Formation et caractérisation d'un nuage froid de molécules diatomiques de césium.. Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2000. Français. ⟨tel-00600313⟩

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