PhD in Physics
Thesis defended on 1st December 2017
PhLAM laboratory


Title and abstract

Spectroscopic study of terpenes of atmospheric interest, and of their oxidation products and associated hydrates.

The synergic combination of Fourier transform microwave spectroscopy coupled with a supersonic jet and quantum chemical calculations allows us to study the molecular structure and the conformational landscape of molecules in the gas phase, isolated or in small aggregates.
In the present work, we have applied this approach to analyze the structure of molecules of atmospheric interest, i.e. monoterpenes (C10H16), which are known to be precursors of atmospheric aerosols. Likewise, we have studied their oxidation products as well as their hydrates.

The pure rotational spectrum of three bicycles, camphene, β-pinene and α-pinene have been recorded, including all their 13C isotopologues and analyzed. Then, we have determined their gas phase molecular structure, with the support of ab initio and DFT calculations.
In like manner, we have characterized the conformational landscape and the rotational spectra of two oxygenated monoterpenes: nopinone (C9H14O) and fenchol (C10H18O). We have demonstrated that the geometrical structure of nopinone, an oxidation product of β-pinene, is not altered. For fenchol, the most stable conformers of the two stereoisomers endo- and exo- were identified and characterized. The second part of the Thesis has been dedicated to the study of hydrates of nopinone and fenchol. As a result of the upgrade of the instrumentation, using our state-of-the-art spectrometer, we were able to exhibit the first steps of the microsolvation of these molecules. Based on theoretical calculations, we have characterized the most stable mono-, di- and tri-hydrates. We have also observed that the hydration sites depend on the functional groups of the molecule.

Keywords: terpenes-oxidation, hydration, conformational analysis, molecular spectroscopy, ab initio method, density functional, molecular structure, atmospheric aerosol.

Laboratory: PhLAM (Physique des Lasers, Atomes et Molécules, UMR8523)

Financing: Université Lille1 - Labex CaPPA

Thesis supervisor(s): Prof. Thérèse HUET (Univ. Lille 1)

Referees: Dr Pierre ASSELIN (CNRS / UPMC) et Dr Isabelle KLEINER (CNRS / Univ. Paris 12)

Examiners: Dr Pascal DRÉAN (Univ. Lille 1), Prof. Denis PETITPREZ (Univ. Lille 1) et Dr Olivier PIRALI (CNRS / Univ. Paris 11)