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Detection of a Giant Molecule

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Directeur de thèse /Supervisor : Martina Knoop
Coordonnées/Email and address : martina.knoop, Tel
Co-encadrant /Co-advisor : Christophe Jouvet Christophe.jouvet

Description du sujet /Abstract :
A laser-cooled cloud of trapped ions is an example of a non-neutral plasma, and behaves in some aspects as a cold charged fluid. The interaction of a heavy molecule that crosses the cloud of trapped atomic ions, and in particular the energy exchange with the ion cloud, modifies the temperature of the trapped atomic ensemble. This variation has direct impact on the observed fluorescence of the cloud, which can therefore serve as detector of the heavy and rather slow molecule. This original and non-destructive detection process is also valid for charged molecules with masses higher than 100 000 amu, which cannot be directly detected today. Actually, existing detectors fragment these large molecules and detect the fragments.
In our experimental set-up, the detection signal is based on the variation of the monitored fluorescence of a laser-cooled ion cloud, during (and after) the crossing of a single, charged molecule. The molecule which is not affected by the trapping fields, can be recycled after its crossing of the cloud. This detection method is very versatile and can apply to atoms, molecules and even nanoparticles, but it is in particular interesting for giant molecules, as for example viruses which are at present not directly detected. Our numerical simulations predict that even the charge state of the molecule can be resolved (e.g. distinction between a singly-charged and a doubly-charged molecule). We have patented the detection process and the experimental prototype is in the testing phase.
We offer an experimental thesis in an exciting stage of the project, now that the set-up is up and running. Ions are trapped, different molecules are tested, and the overall parameter space is to be explored and optimized. The candidate should have good competences in atomic physics, laser and optics, and some curiosity for plasma physics and/or physical chemistry. He or she should also be motivated for experimental physics, and the work in an interdisciplinary research team.