ChAracterizating the Spectral Signatures of astrO-relevant carbonaceoUs cLusters Experimentally – CASSOULExp

Cosmic dust plays a crucial role in the physical and chemical evolution of the interstellar medium. It exists an abundant population of nanometer size grains (named nanograins) which have a high surface over volume ratio. These nanograins are expected to be strongly coupled to the gas phase and to contribute to its chemical enrichment. Up to now, gas-grain interactions have been studied by using “infinite” surfaces and therefore cannot account for size and morphology effects specifics to these nanograins. The CASSOULExp project aims to study cationic clusters composed of polycyclic aromatic hydrocarbons and water molecules as a model case of interactions between water molecules and carbonaceous nanograins expected to exist in planet and star forming regions. In order to characterize these systems, we will develop a methodology able to systematically measure the infrared spectral signatures of these clusters as a function of the nature and the number of molecules that composed them. Moreover, we will study the modifications of these spectra as a function of the cluster temperature in order to explore desorption and molecular diffusion mechanisms. We will be carrying out this project using PIRENEA 2, a unique setup in laboratory astrophysics, which will enable to produce these clusters, thermalize them, isolate them under astrophysical conditions and measure their action spectrum in the infrared. These new data will allow us to propose families of nanograins organized according to the observed spectral trends with respect to the experimental parameters. This will be of high interest to constraint quantum chemistry models and these results will be useful to interpret astrophysical observations, notably those performed by the James Webb Space Telescope. This project will open the path to more complex studies regarding other spectral or temporal domains performed on molecular or atomic clusters which have a high interest in astrochemistry or atmospheric chemistry.