Excited-State Dynamics in Open-Shell Molecules

Abstract : In this thesis the excited-state dynamics of radicals and biradicals were characterized with femto-second pump-probe spectroscopy. These open-shell molecules play important roles as combustion intermediates, in the formation of soot and polycyclic aromatic hydrocarbons, in atmospheric chemistry and in the formation of complex molecules in the interstellar medium and galactic clouds. In these processes molecules frequently occur in some excited state, excited either by thermal energy or radiation. Knowledge of the reactivity and dynamics of these excited states complete our understanding of these complex processes. These highly reactive molecules were produced via pyrolysis from suitable precursors and examined in a molecular beam under collision-free conditions. A first laser now excites the molecule, and a second laser ionizes it. Time-of-flight mass spectrometry allowed a first identification of the molecule, which was completed by the photoelectron spectrum. The photoelectron spectrum was obtained via velocity-map imaging, providing an insight in the electronic states involved. Ion velocity map imaging allowed separation of signal from direct ionization of the radical in the molecular beam and dissociative photoionization of the precursor. During this thesis a modified pBasex algorithm was developed and implemented in python, providing an image inversion tool without interpolation of data points. Especially for noisy photoelectron images this new algorithm delivers better results.
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  • HAL Id : tel-01576556, version 1

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Anja Röder. Excited-State Dynamics in Open-Shell Molecules. Theoretical and/or physical chemistry. Université Paris-Saclay; Julius-Maximilians-Universität (Wurtzbourg, Allemagne), 2017. English. ⟨NNT : 2017SACLS099⟩. ⟨tel-01576556⟩

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