Adsorption and femtosecond dynamics of CO molecules adsorbed on epitaxial nanoparticles : non-linear optical probe, size and support effects
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access URL: https://theses.hal.science/tel-00692450
format: HTML
issued: 2026-05-20T10:58:55.126129
modified: 2026-05-20T10:58:55.043221

test_moissonnage_selune
type: Agent

Adsorption and femtosecond dynamics of CO molecules adsorbed on epitaxial nanoparticles : non-linear optical probe, size and support effects
type: Dataset
contact point: Organization
  fn: CCSD
keyword: pump-probe
keyword: nanoparticles
keyword: femtosecond-lasers
keyword: nanoparticule
keyword: laser-femtoseconde
keyword: thin-oxide-layer
keyword: couche-mince-doxyde
keyword: pompe-sonde
keyword: chimisorption
keyword: theses
keyword: physcondcm-genphysics-physicscondensed-matter-cond-matother-cond-matother
keyword: photodesorption
keyword: infoeu-reposemanticsdoctoralthesis
keyword: polarisabilite-vibrationnelle
keyword: vibrational-polarizability
keyword: chemisorption
keyword: sfg
landing page: https://theses.hal.science/tel-00692450
description: We have studied the spectroscopy and excitation dynamics of a hybrid system consisting of molecules and nanoparticles (NPs) on insulating layer, which is also a model catalyst (Pd NPs grown on a thin layer of MgO on Ag(100)). We have highlighted the role of the shape and the NPs size as well as the thickness of the oxide layer in the interaction between NPs and CO molecules, by fundamental experiments allowing to differentiate the adsorption sites (Sum Frequency Generation (SFG)). In addition, pump-probe experiments allowed us to probe the dynamics of interaction between the photoexcited electrons bath in the NPs and the molecules. A combined study by LEED and STM allowed us to determine the growing conditions of MgO film. Subsequently palladium NPs were grown on this film with satisfying density and distribution size. The SFG spectra show a strong dependence of the vibrational frequency with the NPs size and the CO coverage. A dipole interaction model was developed showing that the CO frequency shift with the coverage and the NPs size has two causes: the dipolar interaction between molecules on the one hand, which is modeled, and on the other hand the variation of the molecule-substrate chemical bond when the adsorbate coverage varies. The model has allowed us to show that the vibrational polarizability of CO changes by 40 % in our range of NPs size. The decrease in the strength of the chemical bond results in the decrease of the frequency at zero coverage when the NPs size decreases. These variations are consistent with the literature: upon a decrease in the particle size, the electronic DOS decreases, the Pd-Pd bonds contract and the adsorption energy of CO molecules decreases. The electronic excitation of the NPs and the silver substrate manifested by the spectroscopic response and the CO photodesorption. We observed the decoupling of the electronic excitation produced in silver when the thickness of the oxide layer exceeds a few atomic planes. There is a clear …
identifier: NNT: 2012PA112014
issued: 2026-05-20T10:58:55.088751
language: fr
modified: 2026-05-20T10:58:55.088758