Réponse linéaire dynamique et auto-cohérente des atomes dans les plasmas quantiques : photo-absorption et effets collectifs dans les plasmas denses

Abstract : In modeling dense and partially ionized matter, the treatment of the free electrons remains an important issue. Compared to bound electrons, the delocalized and non-discrete nature of these electrons is responsible to treat them differently, which is usually adopted in the modelings of radiative properties of plasmas. However, in order to avoid inconsistencies in the calculation of absorption spectra, all the electrons should be described in the same formalism.We use two variational average-atom models: a semi-classical and a quantum model, which allow this common treatment for all the electrons. We calculate the photo-extinction cross-section, by applying the framework of the linear dynamical response theory to each of these models of an atom in a plasma. For this study, we develop and use a self-consistent approach, of random-phase-approximation (RPA) type, which, while going beyond the independent electron response, permits to evaluate the collective effects by the introduction of the dynamical polarization. This approach uses the formalism of the time dependent density functional theory (TDDFT), applied in the case of an atomic system immersed in a plasma.For both models, semi-classical and quantum, we derive and verify in our calculations, a new sum rule, which allows the evaluation of the atomic dipole from a finite volume in the plasma. This sum rule turns out to be a crucial device in the calculation of radiative properties of atoms in dense plasmas.
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Submitted on : Thursday, May 21, 2015 - 9:38:11 AM
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  • HAL Id : tel-01154056, version 1

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Clément Caizergues. Réponse linéaire dynamique et auto-cohérente des atomes dans les plasmas quantiques : photo-absorption et effets collectifs dans les plasmas denses. Physique des plasmas [physics.plasm-ph]. Université Paris Sud - Paris XI, 2015. Français. ⟨NNT : 2015PA112042⟩. ⟨tel-01154056⟩

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