Diversité structurale des agrégats de carbone et d'hydrogène, implications pour les porteurs des bandes aromatiques infrarouges

Abstract : The mid-IR emission of many lines of sight in the Interstellar Medium (ISM) displays Aromatic Infrared Bands (AIBs) commonly attributed to Polycyclic Aromatic Hydrocarbons (PAHs). Identifying AIB carriers would allow for a clearer view of carbon matter evolution in the ISM. We intend to compare AIBs with theoretically derived and expermentally obtained IR spectra of hydrocarbon nanoparticles. The work done here focused on the structural analysis of such systems. Disordered molecular systems containing 24 to 60 C-atoms are generated by multi-tempering Monte Carlo simulations using the empirical potential AIREBO. After quenching the potential energy, the created structures are characterized with various order parameters. The evolution of the structural organization is analyzed as a function size and chemical composition (C/H ratio) of the systems. Generated structures display a great diversity, The statistical study of the order parameters shows tendancies. The global shape of the clusters depends on their size. H-atoms, often found on the edges of cage-like structures, favour a higher degree of organization. The calculation of IR spectra for those structures will be done in the future. To obtain experimental spectra of gas-phase hydrocarbon nanoparticles, the development of the IR emission spectrometer FIREFLY was continued. FIREFLY was coupled with a source of nanoparticles. Thoses developments will soon allow to measure experimental spectra of the molecular systems of interest.
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Maëlle Bonnin. Diversité structurale des agrégats de carbone et d'hydrogène, implications pour les porteurs des bandes aromatiques infrarouges. Agrégats Moléculaires et Atomiques [physics.atm-clus]. Université Paris-Saclay, 2018. Français. ⟨NNT : 2018SACLS156⟩. ⟨tel-02175729⟩

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