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Measuring Interstellar Reactions of Aromatics by Gas-phase Experiments

Periodic Reporting for period 1 - MIRAGE (Measuring Interstellar Reactions of Aromatics by Gas-phase Experiments)

Reporting period: 2019-05-01 to 2021-04-30

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.
Work was conducted via 5 work packages (WPs). WP1 sought to train the fellow and to build skill with new research techniques and methodologies, as well as to effectively manage the project. The fellow was effectively trained by the supervisor and other researchers in the operation and theory of three new experimental techniques. The supervisor worked with the fellow to provide training in project management. WP2 involved instrument and experimental design and, combined with WP3 (Laboratory data collection and Analysis), yielded four publications and eight scientific presentations.

WP4 sought to train the fellow in a new area and to link laboratory data with observational astronomy. This work package resulted in certified training for the fellow (GBT remote observing certification), a new network of collaborators and 3 peer-reviewed publications. The fellow also visited the University of Bordeaux where she was trained by a world leader in astrochemical modelling, allowing her to better exploit the laboratory data obtained during the fellowship period. These training experiences and publications exceeded the goals outlined in the grant agreement. Results of this MSCA are reported in peer-reviewed publications in the Astrophysical Journal Letters (x3), Science, The Journal of Physical Chemistry, The Journal of Quantitative Spectroscopy and Radiative Transfer and ACS Earth and Space Chemistry. These journals span a wide range of disciplines from chemistry to astronomy, consistent with the truly interdisciplinary nature of the research that was conducted. The data that was collected during this action will inform and enhance further publications in the years to come, in addition to the ones published during the fellowship itself.

WP5 focused on communication and dissemination of the results. The fellow presented the results of the action at conferences, online seminar series and at department colloquia. The fellow also was involved in several engagement activities to disseminate the results of the MSCA to the general public including Twitter posts, an exhibition at the Fête de la Sciences, an interview published in the magazine Sciences Ouest and a prize-winning poster.
This MSCA allowed the fellow to develop agility with many different research methodologies, including several areas across chemistry and astronomy in which she had no prior training. During the fellowship, a new technique in the field of chemical kinetics was developed that will have far-reaching implications outside of the goals of the action.

The MSCA resulted in the first detection of individual polycyclic aromatic molecules in interstellar space. This detection was published in Science and was highlighted in several press releases and on popular science news websites, capturing public interest. The detection of PAHs in space will be high impact and will motivate and inspire new directions in laboratory experiments, modelling and astronomical observations.

The fellow has transferred knowledge to students and colleagues in France and the USA that will spread across the various research fields and sectors in which they will be employed. The fellow engaged with underrepresented minorities in STEM during the course of the fellowship via two online workshops, actively promoting diversity in academia and increasing visibility for women in astronomy and chemistry.
A broad impact is enhanced public perception of physical chemistry and astrochemistry as an accessible and exciting field, which has been achieved through effective communication efforts despite the impact of Covid-19.
The MSCA fellow in the laboratory in Rennes
The experimental setup in Rennes built and operated during the MSCA
The Green Bank Telescope, where the fellow was trained to search for molecules in space