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M/F Laboratory investigation of water-carbon nanograin interactions of astrophysical interest

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General information

Reference : UMR5589-CHRSOU-001
Workplace : TOULOUSE
Date of publication : Friday, September 04, 2020
Scientific Responsible name : Sébastien Zamith
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

This PhD project in the field of laboratory astrophysics aims at studying the evolution of analogues of carbonaceous nanograins found in the interstellar medium. These will be formed of mixed aromatics/aliphatics/water molecules clusters controlled in size and temperature and isolated in physical conditions that approach those found in astrophysical environments. Their evolution under collisions with atoms/molecules and/or under UV photon irradiation will be investigated.

The experiments will be carried out on two complementary experimental setups. On one hand, the versatile aggregation cluster source at LCAR, which has been developed for collision induced dissociation experiments and measurements of the evaporation rate of size-selected clusters [1]. On the other hand, the PIRENEA 2 setup, built in the framework of the ERC Synergy Nanocosmos project [2], combines a cryogenic environment with a variety of ion trapping techniques in order to study molecular processes in conditions that approach those encountered in interstellar molecular clouds.

More specifically, the PhD project consists in studying the properties of small mixed clusters composed of polycyclic aromatic hydrocarbons (PAHs) (methylated PAHs) and water molecules, (PAH)n(H2O)m, m,n=1-10. The candidate will first optimize the source conditions to produce the species of interest and carry out collision induced dissociation experiments using the Cluster group experimental setup. He/she will then produce the same species in PIRENEA 2 using a duplicate of the aggregation source. He/she will study the interaction of the mixed complexes with photon irradiation in the UV-visible range, exploring desorption processes and the possible formation of new molecular species by photochemistry. These processes will be studied as a function of the irradiation wavelengths as well as the size, stoichiometry and initial temperature of the clusters, which can be tuned between 10 and 300 K. To get further insights into these processes, the project will benefit from complementary theoretical studies that will be carried out by the MAD team at LCPQ [3].

The confrontation of the obtained data with astronomical data from the coming James Webb Space Telescope (launch planned in fall 2021) will be favored by the strong involvement of the MICMAC team at IRAP in JWST observations [4].

This doctoral work will take place in an interdisciplinary context combining cluster physics, physico-chemistry and astrophysics. It will benefit from the synergy between several research teams with complementary skills: the MICMAC department at IRAP (laboratory astrophysics and astronomical observations), the LCAR Cluster team (experimental physics) and the MAD team at LCPQ (simulations of quantum physics).

The candidate is expected to have a degree in molecular physics and willingness for experimental physics involving cryogenic ion traps and laser spectroscopy. Knowledge in astrochemistry and quantum chemistry will be necessary and could be completed, if necessary, during the PhD period.

[1] I. Braud, S. Zamith, and J.-M. L'Hermite, Rev. Sci. Instrum. 88, 43102 (2017)
[2] A. Bonnamy et al., 2018, https://nanocosmos.iff.csic.es/technology/pirenea-2-pirenea-and-espoirs-upgrades/
[3] E. Michoulier, N. Ben Amor, Mathias Rapacioli, J. A. Noble, J. Mascetti, C. Toubin, A. Simon, Phys. Chem. Chem. Phys. 20, 11941-11953 (2018)
[4] Programme “Early Release Science” (ERS) intitulé “Radiative feedback from massive stars”; www.jwst-ism.org

Work Context

The Laboratoire Collisions Agrégats Reactivité (LCAR) is a joint research laboratory of 41 people, with support from both CNRS Institute for Physics and University of Toulouse III. LCAR's activities take place on the Toulouse III University campus.

LCAR brings together six research teams, one theoretical and five experimental, whose work is dedicated to fundamental research. These research teams are divided into two main areas: "molecular physics" and "laser-matter interaction". Since 2015, two experiments carried out by a team from the Institute for Research in Astrophysics and Planetology (IRAP) have been hosted at LCAR and significant synergies have been formed between this team and the molecular physics teams of LCAR.

The thesis will take place in an interdisciplinary context combining cluster physics, chemical physics and astrophysics. It will benefit from a synergy between several research teams with complementary skills: the MICMAC department of IRAP (laboratory astrophysics and astronomical observations), the LCAR cluster team (experimental physics) and the LCPQ MAD team (simulations of quantum physics).

The doctoral work will take place at LCAR on joint experiments carried out by the cluster team from LCAR and MICMAC group from IRAP. The student will be co-supervised by Christine Joblin (DR CNRS IRAP) and Sébastien Zamith (CR CNRS LCAR) in a team of ½ dozen people.

Constraints and risks

The candidate is expected to have a degree in molecular physics and willingness for experimental physics involving cryogenic ion traps and laser spectroscopy. The subject is part of an interdisciplinary context involving astrophysicists and theoreticians in molecular physics. Knowledge in astrochemistry and quantum chemistry will be appreciated and could be completed, if necessary, during the PhD period.

Additional Information

To apply, please provide a CV, a cover letter and the contact details of three referents.
The position is for a period of 3 years starting at fall 2020.

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