The ASTROROT research program was very successful, with twelve studies being published in international, peer-reviewed scientific journals so far; several further publications are still in preparation. Furthermore, it was central to establish high-level and fruitful collaborations in the astrochemistry field.
The results of ASTROROT do significantly foster our understanding of astrochemistry. The research goes far beyond the state-of-the-art: We developed and used cutting-edge techniques in the laboratory. These techniques now enable studies for this important frontier of physics and chemistry that previously would have been prohibitively time-consuming or even impossible. Our studies significantly extended the spectroscopic knowledge of PAHs and of small biomolecules in vibrationally excited states – important tracers in space also with interest for the origin of life. Furthermore, we gained information about new formation pathways of complex molecules at the molecular level by exploring the extreme conditions of plasma sources.
In the following, some highlights are summarized. To spectroscopically characterize the molecules of interest over a broad frequency range, we developed a new broadband rotational spectrometer covering the 18-26 GHz frequency range. This frequency range overlaps with a number of radio telescopes in the world, so that direct laboratory measurements from this range are particularly relevant for the community. This spectrometer is based on the new segmented approach, which is a low-cost approach and thus particularly appealing for smaller groups as well as teaching laboratories, and as such an important dissemination aspect of ASTROROT.
Our studies had a particular focus on organic molecules in astrochemistry that can relate to the long-standing quest to understanding the origin of life. The strength of our approach is that we can cover a large frequency range and thus generate very accurate and precise line lists for radioastronomic searches. There are hypotheses that biomolecules formed in space initiated or fostered the development of life on Earth. Our studies contributed to unraveling the chemical inventory of interstellar space also with respect to potential precursors of the building blocks of life, such as the amino alcohols alaninol, valinol, leucinol, and isoleucinol or imidazole, which is a heteroatomic ring. We provided a detailed spectroscopic characterization of these molecules to search for them in interstellar space, including their rare isotopologues.
In the course of the ASTROROT program, we developed a new research line focusing on the structure and photophysics of polycyclic aromatic hydrocarbons (PAHs). Besides detailed spectroscopic characterizations of PAHs monomers, we also investigated PAH-water complexes, which can provide important insights into the first steps of ice grain formation. These results gained significant attention also beyond the astrochemistry community, because such ice grains are understood to be at the heart of a rich chemistry in space.
Using different light sources, we also investigated the photophysics of PAHs, where we found interesting ultrafast break-up processes of these molecules upon harsh radiation. Using the plasma environment of an electric discharge source, we studied the interplay between bottom-up vs. top-down processes. The results are supporting the high chemical flexibility in space and the importance of bottom-up and top-down processes.
