One of the major questions in modern physics is how life emerged on Earth and whether it is a general characteristic of our Universe. In addition to its own interest, understanding molecular complexity in space helps to understand the link between the young Solar System and its small bodies, in which today we detect complex molecules and even amino acids (as in comets and meteorites). Where these molecules come from? How and where did they form? What do they tell us about stars and planets formation? And last, but not least, atoms and molecules are the remote thermometers and barometers, as their observed line spectra can and are used to extract a mine of precious and often unique information. Grain-surface astrochemistry is facing new fascinating and challenging questions. Among them, three are particularly relevant for this project: - Is it possible to build a grain-surface chemistry starting from radical blocks, and if so, what will be the chemical routes? - Is the diffusion of radicals fast enough to compete with atom addition (and destruction)? - How to measure radicals in experiments, in realistic conditions ? - Is grain-surface chemistry fully compatible with the astronomical observations and the current astrochemical models? Or in other words, what ISM molecules form prevalently on the grain surfaces and when? Here we propose to join the forces between two groups with complementary laboratory expertise (LERMA and PIIM) and one with astrophysical, observations and modeling, expertise (IPAG). The immediate project goal is to understand how molecules diffuse, meet and mate on the grain surfaces in order to assess what COMs are formed on them and how. To reach it, we will compare dedicated laboratory experiments and include them in a new astrochemical code able, at the end of the project, to compare predictions with observations, and to better understand the role and limits of the solid-state chemistry in space. The work is organized in 3 connected tasks corresponding of our 3 expertises : 1) Diffusion of radicals and building-up molecules on surfaces. It includes i) the optimization of new source of radicals and the measurement of their diffusions ii) the systematic studies of the reactivity of specific chemical groups iii) in order to understand what is the limit of the complexity of COMs synthesized on surfaces 2) An innovative experimental set-up will be implemented at PIIM coupling low-temperature chemistry and electron spin resonance (ESR) to overcome our blindness to intermediate species. Once done, slow reactivity of radical with their molecular environment will be studied, simulating the early stage of ice mantle growth. The final goal is to study radical-radical chemistry that should occur during the formation of stars 3) We will build up a new code, from GRAINOBLE, that is able to simulate the experimental results. Only after this first step, it will be possible to extrapolate the experimental results to the ISM conditions, as well as having a better determination of physical parameters to be included in astrochemical codes. The natural end of this project will be to compare our understanding of the solid-state chemistry to observations, to evaluate its impact on the molecular growth and to diffuse our results.

This experimental project will study the effects of irradiation on the chemistry of Jupiter’s moon Europa. This moon’s surface is subjected to Jupiter’s intense radiation belts (electrons, oxygen, and sulfur). The organic compounds on the surface, of exogenous or endogenous origin, may be processed by radiation; the products of this irradiation may then be returned to the ocean and enrich its chemistry. These processes may be critical to icy moons’ habitability and the interpretation of future space mission data. We will irradiate icy samples (with organic and inorganic compounds) with a beam of electron or sulfur ions. The organic residue of these experiments will be analyzed with infra-red spectroscopy and advanced high-resolution mass spectroscopy techniques to fully characterize them. A complementary analysis will allow to anticipate how the products would appear to future space instruments.

Point defects in crystals occur when an atom is missing or is in an irregular position. After an initial skepticism, they spiked interest because of their possible applications as qubits in quantum computers. A strong and stable photoluminescence at room temperature (RT) and a single photon emission are the needed requirements. Point defects in hexagonal Boron Nitride(hBN) have been experimentally identified as RT stable single photon sources. In the photoluminescence spectrum of hBN there are different emission lines at transition energies ranging over the visible and the UV spectrum, and well-resolved phonon replica at lower energies. Whereas a considerable effort has been made so far and several color centers candidate have already been suggested, their exact nature remains uncertain. This project aims to solve some controversies related to the interpretation of defect related emission lines, with a special care for the study of the local vibrations at the origin of phonon replica.

Secondary Organic Aerosol (SOA) particles in the atmosphere are recognized to affect both climate change and human health. Biogenic SOA (BSOA), which constitutes 30 to 50 % of the global organic aerosol budget, may be present in various particle phase states. To date, the formation and evolution (i.e. the atmospheric aging during air mass transport) of BSOAs have been investigated by performing both field measurements and laboratory experiments, highlighting the complexity of related physico-chemical processes, due to the large diversity of their chemical makeup. Actually, interactions between water vapor and BSOA play key roles in air quality and climate change, requiring an accurate scrutinization. As aerosol particles may be considered as micro-reactors, a key bridge between individual process studies and the complexity of in situ atmospheric chemistry can be provided by lab-single particle investigations. Interactions between gases and particles may be confined to the surface region for particles in solid and semi-solid phases but may also occur in the bulk for particles in the liquid phase. In addition, the condensed water may serve as a reaction medium for multiphasic reactions. The condensed-phase water may be regarded as a plasticizer whose presence results in changes in the particle phase state which may directly impact the molecular diffusion both at the particle surface and in the bulk. Thus, the particle phase state, which is determined by the particle viscosity, has emerged as a research focus during the last decade in the atmospheric science community. So far, most studies on aerosol hygroscopicity, phase states and viscosity have been performed with a focus on laboratory experiments, which demonstrated that atmospheric particles can adopt not only a liquid phase state, but also semi-solid and even solid states, depending on their chemical composition (including inorganic/organic mixing) and on the atmospheric relative humidity. The SOAPHY project aims at deepening our understanding of BSOA-water particle interactions by determining the main physical and/or chemical factors that drive and/or influence the water-particle interactions during atmospheric aging processes at the particle scale. In this project, the main scientific questions to be answered are: what is the influence of chemical transformations, including photochemical reactions, upon induced changes in the composition, chemical heterogeneities, molecular organisation, hygroscopicity behaviour, water diffusion and, ultimately, the particle viscosity at the particle (and/or the surface) level? Special attention will be paid to the role of the particle surface and the inter- and intra-molecular organisation on the viscosity properties of BSOAs. SOAPHY will focus on BSOAs formed from (photo)oxidation pathways of alpha-pinene, as its strong atmospheric representativeness makes it a relevant model system to study biogenic VOC atmospheric fate. Laboratory studies will use a panel of original and complementary on-line and in situ experimental set ups. Investigations on model BSOA particles in ambient conditions will be performed through experiments conducted on single particles either when deposited on substrates or in total levitation. Molecular scale BSOA-water processes will be investigated using low temperature matrix isolation experiments. The outcomes of the SOAPHY project will lead, first, to the proposal of an original experimental device dedicated to individual gas-particle interaction investigations and, second, to novel multiscale concepts including physico-chemical markers related to BSOA-water interaction processes, which will provide key understanding of direct effect of aerosols on climate change and air quality.

In a fusion plasma, ions escape from the plasma core and hit the reactor's walls where they remain implanted. During operation, the walls are hot (~900 K) and while absorbing hydrogen isotopes and helium they also release them. This implantation/degassing process is called recycling. The recycling process affects mainly the tungsten divertor which receives the highest power fluxes (up to 40 MW/m²). The interaction of intense particle fluxes with walls can induce changes in the surface condition and thermo-mechanical properties of plasma facing components and thus affecting the proper functioning of the reactor. For these reasons, in the framework of the LETHE project, we will experimentally study changes in the recycling process induced by He/wall and light/wall interactions. Such studies are necessary to predict how the walls will behave during plasma operation in tokamaks. The experiments will be carried out using an ultra-high vacuum device allowing to characterize the atomic composition of sample surfaces, to implant helium with ion beams or plasma, and to quantify the species trapped in the volume of the materials by using the temperature-programmed desorption technique. Three are the main objectives of the LETHE project: 1. Understanding the physical mechanisms underlying the degradation of materials (e.g. blister formation) and the change in their physico-chemical properties after He implantation/thermo-desorption cycles. Moreover, an in situ spectroscopic ellipsometer, installed in the framework of the LETHE project, will allow to probe the degradation of the surface of materials during ion-surface interaction. 2. The study of the influence of thermal loads in the recycling process and, consequently, on the parameters of the edge plasma. Thermal loads, simulated by a high-power laser, reaching pre-implanted samples, will induce sudden desorption of trapped species which, consequently, will perturb the plasma. The properties of the plasma (e.g. temperature and density) will be measured by a Langmuir probe. 3. Development of an optical method to prevent surface degradation, e.g. blistering, which can lead to plasma disruption.