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Production et transport des états excités du projectile en interaction ion-solide

Abstract : In ion-solid collisions, more excited states of projectile ions with high angular momenta l are populated than in ion-atom collisions. The use of 13.6 MeV/u Ar18+ projectile ions and solid carbon targets allowed us to study Ar17+ excited states initially populated by electron capture. Using various targets with increasing thickness from 3.5 to 200 µg/cm², the evolution of excited states from the single collision condition to the population equilibrium was investigated. We observed the evolution of the Lyman line intensities as a function of the ion transit time inside the target (sensitive to core state population) and as a function of the ion time of flight behind the target (sensitive to Rydberg state population). To explain the experimental results, a complete theorical analysis of the transport of excited states inside the medium was performed. We used two different collisional models. The first one is a rate equation model based on a statistical description of binary collisions of the projectile with target atoms. The second one is a classical transport theory based on an equation describing the motion of the projectile electron on a classical orbit perturbed by a stochastic force. A comparison with experiment shows that a such collisional approach allows to interpret the excited l-state population, but fails in describing the core state population. The observed l mixing in these states is much larger than predicted by the models. The polarization of the medium induced by the projectile ion, with both models do not take into account, could be responsible for this mixing by means of the Stark effect.
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Contributor : Emily Lamour <>
Submitted on : Tuesday, February 4, 2003 - 6:36:48 PM
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  • HAL Id : tel-00002357, version 1


Emily Lamour. Production et transport des états excités du projectile en interaction ion-solide. Physique Atomique [physics.atom-ph]. Université de Caen, 1997. Français. ⟨tel-00002357⟩



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