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Reference : UMR8214-BERUST-008
Workplace : ORSAY
Date of publication : Monday, September 14, 2020
Type of Contract : FTC Scientist
Contract Period : 12 months
Expected date of employment : 1 November 2020
Proportion of work : Full time
Remuneration : according to experience
Desired level of education : 5-year university degree
Experience required : Indifferent
He / she will perform the spectroscopic studies carried out on the Nanograins and Firefly experimental setup. PAHs,fullerenes and soot nuclei are produced using a flat premix flame, the source chamber is coupled either to a time-of-flight mass spectrometer (Nanograins) or to a spectrometer for measuring infrared emission (Firefly). These two sets are surrounded by a large laser park to conduct spectrocopy and dynamic studies. The post-doctoral student will be responsible for carrying out the experiments and analysis, as well as contributing to the supervision of students on these devices. The contract is for one year potentially renewable.
To explain the infrared emission bands (IR) observed in the interstellar medium (ISM), now called aromatic infrared bands (AIB), the presence of large polycyclic aromatic hydrocarbons (PAHs) was suggested 35 years ago. AIB carriers are also suspected of participating in absorption in the ultraviolet (UV) through the wide band observed at 217 nm, dominating the interstellar extinction curve, and in the diffuse interstellar bands (DIBs) observed in the visible part. Despite a large number of experimental and theoretical studies, the exact nature of AIB carriers remains unclear, although their role is important in the physics and chemistry of the ISM. Recently, the neutral C60 fullerene could be identified in IR emission and the cation through 5 DIBs in absorption, confirming the presence of large carbon molecules and the richness of interstellar carbon systems. The work in progress at ISMO is devoted to the experimental study of nanoparticles (~ 1-3 nm) made up of carbon and hydrogen atoms, in the size range of 20 to 200 atoms with mixed hybridization, in as potential candidates for the identification of carriers of AIBs, DIBs and the interstellar UV band. These astrophysical analogues are produced in the laboratory using rich combustion at low pressure, forming distributions of nanoparticles whose spectroscopic signatures are studied. Experimental measurements of the IR emission spectra and UV-visible electronic absorption spectra are carried out on isolated and, as far as possible, cold systems using the experimental devices developed at ISMO.
The position is intended for a young and talented researcher with solid foundations in molecular physics, chemistry-physics or molecular physico-chemistry. Strong experiences in UV / VIS / IR laser spectroscopy and vacuum technology are highly desirable. Knowledge of the astrophysical context and / or physico-chemistry of combustion and laser diagnostics will be appreciated.
The post-doctorant will join the research group « Molecular Systems, Astrophysics and Environment » at ISMO, a large group with a strong involvement in laboratory astrophysics. The comparison between the experimental data and the theoretical results produced within the framework of the ongoing research and the ANR PACHYNO project (2017-2021) will provide information on the structure of nanoparticles and their spectroscopic characteristics. Finally, the comparison with astrophysical spectra will allow us to progress on our understanding of interstellar carbonaceous matter and will provide solid bases to improve dust models in astrophysics.
Constraints and risks
The experimental activities will use chemicals for laser dyes. Lasers (class 4) will be used regularly. The use of a laboratory flame requires the handling of flammable gases.
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