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Sujet de stage / Master 2 Internship

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Spectroscopy and Dynamics of Molecules Embedded in Helium Nanodroplets

Contact: BRIANT Marc, , marc.briant@cea.fr, +33 1 69 08 81 21
The objective of this internship is to identify and understand the fundamental processes that are turned on when a molecule (or a molecular assembly) absorbs light within a helium nanodroplet. These studies are motivated by fundamental physical chemistry considerations on the structure and dynamics of systems with many degrees of freedom.
Possibility of continuation in PhD: Oui
Deadline for application:10/04/2019

Full description:
The internship will focus on fundamental issues in molecular physical chemistry with the aim of unraveling the conformer landscape of molecules with many degrees of freedom (biological molecules often flexible, for example) as well as the influence of the environment on these conformers. The work, essentially experimental, will consist of using superfluid helium droplets as a support to carry out the spectroscopy of the molecule or molecular complexes of which we want to study the structure.
In practice, the helium droplets are generated by nucleation during the supersonic expansion of cooled helium gas. Playing on the conditions of expansion allows to adjust the size of the droplets. The beam then passes through several collisional trapping zones, which allows the molecules studied to be deposited in the droplets, as well as the solvent molecules. A technique developed in our laboratory allows a strict control of the number of deposited molecules. The stoichiometry of the molecular assembly studied in these droplets is therefore well defined. The spectroscopy is performed by the absorption of light of appropriate wavelength by the molecule or molecular complex studied. The molecule thus excited then relaxes its energy to the helium droplet, weakening it and leading to the evaporation of the droplet. Measuring the disappearance of the droplets as a function of the wavelength of the excitation laser then makes it possible to measure the absorption spectrum of the molecule or the molecular complex hosted in the droplet. Such spectra provide important structural information. These experiments can be conducted on several existing experimental devices.
Technics/methods used during the internship:
Molecular spectroscopy Laser Mass spectrometry

Tutor of the internship


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