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Étude théorique de processus cohérents danc les alcalino-terreux

Abstract : Theoretical investigations on the dynamics of coherent excitation and ionization processes in alkaline-earth atoms are reported. Atomic parameters required to the dynamical treatment are calculated with the R-matrix method in combination with the multichannel quantum defect theory (MQDT). We investigate the photoionization yields into three continuum channels of barium observed by Elliott et al in the study of coherent control through two-photon two-color interfering paths resonantly enhanced by an intermediate state. The dynamics studied by introducing an effective hamiltonian is described as an adiabatic process governed by the coherent excitation of the intermediate states. By using a time-dependent MQDT formalism valid in the weak field limit, we analyze the experiment on coherent control of energy and angular distribution of autoionized wave packets performed in calcium by van Leeuwen et al using isolated core excitation from a Rydberg state and optical Ramsey-like pump-probe technique. The dynamics of autoionization processes is investigated by studying the time dependence of radial electron flux created by one or two short pulses with a possible chirp and observed at fixed macroscopic distances from the atom. We develop a new formalism suitable to investigate autoionizing wave packets of narrow resonances created by short and intenses pulses. Resonances are explicitely introduced in the evolution equations. Their energies (positions and widths) in the complex plane, their couplings with continuum channels due to atomic interactions and their couplings with low-lying discrete states induced by the laser field are deduced from the MQDT formulation and are numerically calculated from the poles and the residues of the physical scattering matrix S and of the light shift operator. The relation between these poles and the Siegert states is presented and identification of the resonances is deduced from the corresponding wave functions.
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https://tel.archives-ouvertes.fr/tel-00002556
Contributor : Martial Millet <>
Submitted on : Friday, March 14, 2003 - 11:45:12 AM
Last modification on : Saturday, April 20, 2019 - 1:23:47 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:07:08 PM

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  • HAL Id : tel-00002556, version 1

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Martial Millet. Étude théorique de processus cohérents danc les alcalino-terreux. Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00002556⟩

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