UFR de Physique

Propositions de stages en laboratoire -- M2

Les offres sont actualisées en mai. Par exemple, les offres de stages pour l'année universitaire 2015-2016 seront mises en place en mai 2015, les offres de stages pour l'année universitaire 2016-2017 seront mises en place pour en mai 2016, etc.

Characterization of atmospherically relevant molecules and their hydrates from gas phase spectroscopy and electronic structure calculations

  • Option International « Atmospheric Environnement » du parcours Lumière-Matière
  • Laboratoire: Laboratoire de Physique des Lasers, Atomes et Molécules (PhLAM)
  • Responsable du stage: DREAN Pascal (pascal.drean@univ-lille1.fr, 03.20.43.49.05)
  • Co-responsable(s): Manuel GOUBET, Thérèse HUET
  • Mots clés: Molecular physics, Spectroscopy, VOC, Microsolvation
  • Fiche complète en PDF : Fiche complète en PDF

We propose to study the pure rotation spectra of samples prepared in supersonic jet with a Fourier transform microwave spectrometer. Briefly, a pulsed valve sends into a cavity under vacuum bursts of sample in the gas phase at a supersonic speed, typically 900 m/s. A short and intense microwave pulse polarizes the molecules of the sample when its frequency is resonant with a rotational transition. Once the pulse is switch off, the free induction decay signal (time domain) emitted by molecules during their relaxation is detected. Finally, a Fourier transform of this signal permits to obtain the spectrum (frequency domain). This technique is so far one of the best to characterize molecular complexes (molecules bounded together by weak hydrogen bonds or Van der Waals interactions). In particular, we are interested in how water molecules can bind to volatile organic compounds (VOCs) of the atmosphere. Indeed, the comprehension of the physico-chemical properties of carbonaceous molecules in aqueous medium comes from the analysis of their pure rotation and/or rovibrational spectrum with the support of quantum chemistry calculations. The recording and the modeling of the spectrum of the free molecule lead for example to the experimental identification of the energetically most stable conformations. In a next step, the same study applied to the molecule in the presence of water gives access to the micro-solvation processes and the structural modifications upon hydration. The main objective is to understand, at the molecular level, the processes that lead to aerosol formation. During this project, mainly experimental, rotational spectra of hydrated VOCs will be recorded and analyzed using theoretical simulations based on the appropriate Hamiltonian. It will be also proposed to participate in the development of a new chirped pulse spectrometer.