Conception, construction and validation of scientific instruments to study the spectrum of cold ionic species
Notice bibliographique
Résumé
This doctoral work, carried out at UCLouvain and University of Rennes 1, explored two experimental methods to study molecular ions. These methods are background free photodissociation spectroscopy at UCLouvain, and cavity enhanced absorption spectroscopy at the University of Rennes 1. In both cases, we have developed the scientific instrument from scratch. Regarding the first part, at UCLouvain a pulsed free jet was developed, and it was coupled with two ionization methods. The first is an electric discharge. The second method consisted of using an electron gun. We have also implemented a time-of-flight (TOF) mass spectrometer capable of increasing resolution and consisting of a unit capable of accelerating, gating and re-referencing the ion beam to ground potential. The recorded mass spectra demonstrated the efficiency of the production of protonated water aggregates, other various mixed cationic aggregates, and anions. The first tests were carried out on N2O+. The photodissociation was performed using a frequency-doubled dye laser in the UV range around 323 nm. Laser fragmentation of the parent ion led to the formation of an ionic (NO+) and neutral (N) species. Analysis of the measured spectrum makes it possible to estimate the minimal rotational temperature that we can attain at 40 K. This result is encouraging and suggests the possibility of studying other molecular ions in the near future. The second part of this work, carried out at the University of Rennes 1, consisted of developing an instrument to study molecular species relevant for astrophysics by high-resolution absorption spectroscopy in the visible and near-infrared regions. In particular, the instrument developed will aim to study the large anionic carbon chains (C$^-_3$, C$^-_4$, … C$^-_n$). Due to space charge effects, the density of target species produced in the laboratory is extremely low even in supersonic expansion. An efficient ion source has been developed. The chosen geometry was that of a planar Laval nozzle, adapted to reach a low temperature (40 K). The planar profile is important to have a greater interaction distance between the ions produced and the laser. These ions are produced using a direct current discharge coupled to the nozzle. On the other hand, by using a supercontinuum laser as a wideband incoherent source coupled to a high fineness cavity, we were able to characterize these species by absorption spectroscopy. The absorption spectrum is obtained using a Fourier transform spectrometer. The optimization and development of the instrument consisted of the optimization of the coupling of the laser source and the optical cavity, and then coupling the output into the Fourier transform spectrometer. We successfully measured the static absorption spectra of methane and acetylene to determine the operating parameters of the instrument, and we look forward to record the spectra of different radicals and finally anionic carbon chains.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».