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Studies towards the understanding of the effects of ionizing radiations at the molecular scales (20 to 150 keV H+/H + He Collisions; Dissociative Electron Attachment to Water)

Abstract : This work comes within the scope of recent studies towards a better understanding of the effect of ionizing radiation at the molecular scales on biological systems, initiated by the group IPM of the IPNL in collaboration with the Institute für Ionenphysik of the University of Innsbruck. It is composed of two parts. One presents a new set of coincidence measurements of cross sections for the impact of protons or hydrogen atoms on helium in the energy range 20-150 keV of interest for the radiation biology. It is an archetypal system of interest for the theoreticians and there exists only a few studies on the impact of hydrogen atoms on helium. This study with helium was also motivated for the sake of performing a general test of functioning of the apparatus before investigating more complicated systems. Similar studies were then performed by replacing helium with water and biological molecules of relevance (Uracil, Thymine ...) as target. This constitutes a study of direct effects of fast ionizing radiations on molecules of biological interest. The second part of the thesis deals with another type of ionizing radiations which can be seen as indirect effects of the first fast ionizing radiations studied in the first part. Low energy electrons emission in the energy range 1 to 16eV follows the bombardment of the matter by swift protons/hydrogen atoms; these electrons have in turn an ionizing influence on the environment. A review of the dissociative electron attachment to water was undertaken in the University of Innsbruck motivated by the existing discrepancies between old studies on the same subject. A special attention was given to the problem of high energy kinetic ion discrimination in the trochoïdal monochromator used for this work.
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Submitted on : Friday, March 31, 2006 - 10:02:56 AM
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B. Coupier. Studies towards the understanding of the effects of ionizing radiations at the molecular scales (20 to 150 keV H+/H + He Collisions; Dissociative Electron Attachment to Water). Nuclear Theory [nucl-th]. Université Claude Bernard - Lyon I; Université Leopold Franzens d'Innsbruck, 2005. English. ⟨tel-00012069⟩

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