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Reference : UMR6294-IOASCH-002
Workplace : LE HAVRE
Date of publication : Friday, July 17, 2020
Scientific Responsible name : Ioan F. SCHNEIDER
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
The dissociative recombination, the ro-vibrational excitation and the dissociative excitation of molecular cations are complex reactive collisions, subject of overlap between two or further fragmentation continua (of ionization and of dissociation type) of neutral molecules [1-4]. These processes, strongly non-Born-Oppenheimer, involve super-excited molecular states, which induce large amplitude resonances in the shape of the cross section. In order to study theoretically their dynamics, we use methods based on the Multichannel Quantum Defect Theory (MQDT) [5-7] and on the R-matrix technique . This latter technique also provides an alternative for the production of potential energy surfaces of the electronic states and their mutual interactions, complementary to the “traditional” quantum chemistry methods, restricted to ground or weakly excited states .
Our theoretical approaches are constantly tested by the comparison of our results with those emerging from the collision experiments, namely in the heavy-ions storage rings . To improve the precision of our state-to-state cross sections in order to keep up with the experimental progress – rotational effects, capture into core-excited Rydberg states, branching ratios – will be one of the objectives of the thesis.
The production of cross sections and of rate coefficients for these processes is of major importance for the kinetic modeling of gaseous cold media. The molecular hydrogen cations and the hydride cations are of huge interest since they are present in two recurring contexts in which we actively work, within a long time collaboration with the laboratories CORIA (Saint Etienne de Rouvray/Rouen) and CIMAP (Caen) of Normandie Université, members, like LOMC, of the LabEx EMC3.
The first context is that of the plasma edge of the fusion devices, related to the ITER project. The hydrogen (H), namely its heavy isotopes deuterium (D) and tritium (T) forming the fuel of the fusion reaction, the molecular cations containing them – H2+, HD+, etc. - are very abundant close to the tokamak walls. The bombardment of these walls – which in ITER will be made by tungsten (W) and beryllium (Be) – by hydrogen and by its heavy isotopes generates, by erosion, hydrides of these metals (BeH+, BeH2+, etc…). On the other hand, the fusion plasma contains “impurities” – atoms or molecules of N, Ne, Ar, C and He – this latter one formed within the fusion reaction. These species interact with H, D, T and produce NH+, ArH+, CH+, HeH+ etc., and their isotopologues (ND+, ArD+, CD+, etc.).
Many of the cations invoked above are present also in the planetary atmospheres and in the interstellar media, and their study will be performed in this second context too. These ions, as well as other, more complex - N2H+, CmHn+ (m, n = 1,2,3…), etc. – are abundantly formed by reaction between hydrogen – atomic or molecular, neutral or ionized – ant the systems containing nitrogen, argon, carbon, etc..
LOMC (Laboratoire Ondes et Milieux Complexes, Laboratory Waves and Complex Media) is an “Unité Mixte de Recherche” (Mixt Research Unit) – UMR6294 – under double authority: CNRS (Centre National de la Recherche Scientific, National Center of Scientific Research) and Université Le Havre Normandie – part, together with other Academic institutions from Caen and Rouen, of Normandie Université. The proposed PhD thesis, having the label of Ecole Doctorale (Doctoral School) ED591 PSIME (Physique, Sciences de l'Ingénieur, Matériaux, Energie) will be performed at LOMC in the group « Reactive Processes », under the supervision of Ioan F. Schneider. It will be also co-supervized by Dr Arnaud Bultel, groupe « Physical Chemistry of Plasma Environments » of CORIA (Complexe de Recherche Interprofessionnel en Aérothermochimie) UMR 6614, Saint-Etienne du Rouvray (scientific campus of Université de Rouen Normandie, Normandie Université). It will take place in the frame of the collaboration of these two laboratories with CIMAP-UMR6252 of Caen, and with laboratories of Université Paris-Saclay, University of Central Florida at Orlando (US), University College London (UK), ATOMKI Institute of Debrecen (Hungary), ISTP-CNR of Bari (Italy), as well as Politehnica and West Universities of Timisoara (Romania).
The Reactive Processes group from LOMC has a powerful computing capacity : on one hand high-performance servers and access to regional and national computing centers - CRIANN, IDRIS - and, on the other hand, to high-performance scientific codes of quantum chemistry and electronic scattering - MOLPRO, QUANTEMOL.
Constraints and risks
There is no particular risk related to the working environment at LOMC, the activity of the PhD researcher being exclusively of theoretical nature. From the scientific point of view, the inherent risks are related to the methods used, in particular on the quality of the molecular data serving for the modeling of the quantum dynamics.
The young researcher should have a master degree in Physics or Chemistry, with a strong motivation and skills for calculus, numerical methods and programming. He should be able to write and conduct scientific projects, to be independent and ready to collaborate. The interested candidates have to provide a complete CV mentioning two reference persons which may be contacted by the supervisors and a detailed motivation letter. The deadline of the application is August 5 2020.
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