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Étude femtoseconde de la dynamique électronique
et vibrationnelle de nano-objets métalliques
et de l'ordre local dans les verres

Abstract : In this Ph.D. work we have investigated the electronic and vibrational properties of metallic nanoobjects as a function of their size, shape and composition, and studied the vibrational modes in glasses, using femtosecond time-resolved spectroscopy. In mono-metallic copper clusters, acceleration of the electron-lattice energy exchanges for sizes smaller than 10 nm has been demonstrated, confirming previous results in gold and silver clusters. The small size regime, i.e., nanoparticles smaller than 2 nm, has been addressed. The results show the limit of the classical confined material approach. In bi-metallic clusters, electron-lattice interaction has been shown to reflect their composition for gold-silver materials, but exhibits a more complex behavior in the case of segregated nickel-silver particles. The impact of shape, structure and environment on the acoustic vibrations of metallic nano-objects has also been studied. Measurements performed in ensemble or pairs of prisms yielded evidence for local fluctuations of their coupling with the substrate. Nano-structuration effects have been demonstrated in nano-columns and segregated components. The vibrational modes associated to local order in glasses have been investigated using a high sensitivity impulsive stimulated Raman scattering technique. The « defect modes » of normal and densified silica, associated to vibrations of ring structures, have been observed and characterized, yielding information on the evolution of the ring density. Performing similar measurements in germania, we have demonstrated the existence of a vibrational mode due to a similar ring structure and determined its characteristics.
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https://tel.archives-ouvertes.fr/tel-00196959
Contributor : Julien Burgin <>
Submitted on : Friday, December 14, 2007 - 7:05:09 AM
Last modification on : Monday, January 22, 2018 - 11:02:02 AM
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Julien Burgin. Étude femtoseconde de la dynamique électronique
et vibrationnelle de nano-objets métalliques
et de l'ordre local dans les verres. Physique [physics]. Université Sciences et Technologies - Bordeaux I, 2007. Français. ⟨tel-00196959⟩

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