Ionisation et défaut Compton : étude de structures moléculaires

Abstract : In both cases of X ray or electron inelastic scattering from atomic, molecular or solid targets, the comparison between the experimental data and the calculations in the framework of the impulse approximation, displays discrepancies or Compton defects. In order to take this effects into account, a theoretical model has been proposed. It allows to write the Compton profile as a sum of terms alternatively symmetric and antisymmetric in q, the parameter of the Compton profile. The leading term of this series corresponds to the profil in the impulse approximation, the other terms give us corrections to this approximation. In the case of the molecular hydrogen, we have calculated the first corrective term. This term arises from the interactions between the remaining ion and the ejected electron. Theseinteractions induce a shift of the maximum, in the energy scale. The correction depends also on the relative orientation of the molecular axis versus the momentum transferred by the incident particles. The study of directionals results allows to display the importance of the anisotropy of the defect, for weak momentum transfer. On the over hand, we have study the effect of chemical bonding on the Compton defect, comparing the defect of the molecular hydrogen with other isoelectronic targets (helium and two free hydrogen atoms). Finally our results are in exellent agreement with the experiment although we have use very simple wavefunctions to describe the initial target state and approximate the bielectronic interaction with a effective charge
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Myriam Roeth. Ionisation et défaut Compton : étude de structures moléculaires. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 1995. Français. ⟨NNT : 1995METZ002S⟩. ⟨tel-01776869⟩

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