CE30 - Physique de la matière condensée et de la matière diluée

Formation and Reactivity of carbonaceous Aerosols in Planetary Atmospheres – FRAPA

Submission summary

The objective of FRAPA project is to better understand the physical and chemical evolution of the atmospheres of planets/moons (e.g. Earth, Titan) and the particle distribution in the interstellar medium . For this it is essential to study the formation, growth and destruction mechanisms occurring in carbon-containing nanoparticles after interaction with ionising radiation. The sizes of carbonaceous particles cover a very large range, from large molecules to nanometer-sized systems. On Earth, Polycyclic Aromatic Hydrocarbons (PAHs) are produced in incomplete combustion and they are key intermediates in the inception and growth of soot particles. In space, carbon particles are primarily formed in the outflows of carbon rich stars, where small carbon chains grow to polycyclic aromatic hydrocarbons or fullerenes. In this bottom-up process these molecules nucleate into larger PAH structures and finally into nanoparticles. However, the origin of the large carbonaceous species and initial heterocyclic skeletal structures of astrophysical nitrogenated or oxygenated PAHs is still unclear. In particular, there is a clear lack of information about ion induced processes in complex nanometric systems.

In the present project, we propose to study particle growth and destruction mechanisms induced by ions colliding with loosely bound C-containing clusters (pure and mixed PAH clusters with water, or ammonia, small hydrocarbon molecules). This requires the development of a novel pump-probe experimental set-up which allows to prepare complex targets and to clearly identify the final reaction products by mass spectrometry (with two ionising beams: ions as a pump and photons as a probe). The aim is to obtain detailed information (size, structure, stability-lifetime od selected species) of the ion-induced reaction products. The project will benefit strongly from theoretical support (in collaboration with LCPQ, Toulouse and UAM, Madrid) and the availability of different beam lines at the GANIL facility (Grand Accélerateur National d’Ions Lourds, Caen, France) allowing to study fragmentation and reactivity of such systems in a very large range of ion kinetic energies from keV to GeV. Thus, different mechanisms due to potential energy, nuclear stopping and/or electronic excitation and ionisation can be probed, mimicking the interaction with solar wind or ions trapped in the Jupiter magnetosphere and cosmic rays. Moreover, we plan to study nucleation of aerosols/grains.

In summary, the proposed studies provide answers to open questions on ion-induced fragmentation dynamics and reactivity of complex molecular systems (e.g. growth, formation of new molecules). These studies are expected to contribute to advances in the fields of astrophysics and astrochemistry (e.g. formation of prebiotic molecules and dust formation) as well as in the field of atmospheric research (nucleation phenomena, aerosol formation, ageing of nanoparticles).

Project coordinator


The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.



Help of the ANR 338,752 euros
Beginning and duration of the scientific project: March 2019 - 48 Months

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