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The Interactions of Particles and Matter (IPM) group studies the out-of-equilibrium dynamics of molecular aggregates under irradiation. Molecular aggregates are present in the Earth’s atmosphere as well as in the astrophysical context. To observe the interactions between molecules under extreme conditions, i.e. at low temperature and subjected to radiation, provides access to the first stages of the formation of atmospheric aerosols as well as the formation of the prebiotic molecules necessary for the appearance of living organisms.

To observe the processes involved at this nanometer scale, the team has built the DIAM (Molecular Aggregate Irradiation Device) platform at IP2I. This highly accurate “drip by drip” allows us to observe, nanodroplet by nanodroplet, the thermalisation that follows irradiation, with repetition allowing us to carry out statistical analyses. These nanodroplets are small model systems composed of a controlled number of molecules of interest. The first experiments on pure water nanodroplets led to the discovery of high-speed evaporation of molecules before complete thermalization in the nanodroplet.

DIAM is thus a probe of the nanoscale thermalisation mechanisms underlying phenomena observed on a global scale.