| Titre : |
Collision induced dissociation of polycyclic aromatic hydrocarbons in a quadrupolar ion trap : Differentiation of isomeric structures in cosmic dust components |
| Type de document : |
these |
| Auteurs : |
Mickaël Carlos, Auteur |
| Editeur : |
Toulouse : Université Paul Sabatier |
| Année de publication : |
2020 |
| Importance : |
152 P. |
| Langues : |
Anglais (eng) |
| Catégories : |
THESIS
|
| Index. décimale : |
THESIS |
| Résumé : |
Polycyclic aromatic hydrocarbons (PAH) are large carbonaceous molecules that are the subject of investigation in various fields from astrochemistry to environmental science. Being a major constituent of cosmic dust, they play a key role in regions of star formation, where their infrared emission is excited by ultraviolet photons. However, the mechanisms involved in their formation remain poorly understood. In simulation experiments in the laboratory as in meteorites, the mass m/z = 202.08 corresponding to the species C_16H_10, has been identified as a key species in the growth of these PAHs. This chemical formula includes several isomeric structures that need to be differentiated. We used the AROMA molecular analyzer to study the differentiation of C_16H_10 isomers by collision-induced dissociation (CID), in the case of fluoranthene and pyrene (two compact structures) and that of9-ethynylphenanthrene (structure with an alkyl group). The various experimental parameters control-ling the CID were explored in order to determine optimized conditions for our experimental conditions. At low collision energy, we have shown that the criterion of 50 % dissociation of parent ions can be used to differentiate condensed from non-condensed structures but is more difficult to differentiate between condensed structures. The procedure has been applied to individual species, their mixtures, and more complex samples of meteorite (Allende) and laboratory analogues of cosmic dust (dusty plasma). We have modeled the dynamics of the ions in the trap and extracted frequency and energy distributions of collisions. The competition with the dissociation rate was treated by Monte Carlo method. The model fit of the pyrene dissociation curve quantified the parameter êta of transfer of kinetic energy into internal energy. The fluoranthene dissociation curve could be modeled using the same values for êta. Finally, we were able to determine the dissociation rate of 9-ethynylphenanthrene, which is not yet known. |
| En ligne : |
https://theses.hal.science/tel-03227791v1 |
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