Astrochemistry is a thriving research field that links together the seemingly disparate disciplines of chemistry and astronomy. Terrestrial chemistry is dominated by aromatic molecules (especially stable rings of carbon and hydrogen), which frequently serve as the building blocks of polymers and many biological compounds. Despite this, at the beginning of this MSCA in 2019, only one aromatic molecule, benzonitrile, had been detected in space using radio astronomy. Benzonitrile provides a key link to benzene, which may be a low-temperature precursor to polycyclic aromatic hydrocarbons (PAHs); molecules that are expected to be lurking in interstellar space but have eluded detected. The presence of aromatic molecules at very cold temperatures (around -263 °C) in interstellar space is difficult to explain.
The MSCA EU-funded project MIRAGE (Measuring Interstellar Reactions of Aromatics by Gas-phase Experiments) aimed to measure chemical reactions of aromatic molecules, such as benzene, down to the low temperatures found in interstellar space. To do this, we combined the expertise in measuring low-temperature reactions in Rennes with a new technique (one of only a few in development worldwide) that uses microwave spectroscopy, the same kind of detection technique used in radio telescopes. The first objective of the action involved building and optimizing this new technique for the measurement of reaction products down to temperatures as low as those in interstellar space. This work is ongoing but has already resulted in a publication, with three more in preparation. The second objective was to use the world-class facilities already available in Rennes to measure how fast reactions between benzene and radicals proceed at low temperature and which products they form. This work resulted in three publications in both astronomy and chemistry journals.
To best exploit the laboratory data collected in this MSCA, the fellow was trained by leaders in radio astronomy and astrochemical modelling, greatly expanding her skillset and promoting cross-disciplinary knowledge exchange. This training allowed her to aid in the search for other aromatic molecules in cold interstellar space, leading to the first detection of individual PAH molecules.
