How Do Organic Molecules Survive in Space?

The discovery of small polycyclic aromatic hydrocarbon (PAH) molecules in interstellar clouds through radio astronomy and observations of infrared (IR) emission bands from PAHs with unprecedented sensitivity by the James Webb Space Telescope (JWST) is opening up a new era for laboratory investigations of PAH unimolecular dynamics.

The general consensus is that PAHs are widespread in space, with data from the Spitzer Space Telescope and JWST supporting that up to 20% of Galactic carbon is present as PAHs . To date, fewer than ten specific PAH-based molecules have been discovered in space. In all cases, identifications were made in Taurus Molecular Cloud 1 (TMC-1) through the comparison of observed rotational lines with spectra recorded in the laboratory [2–5].

However, the observed abundances of these PAHs (1-cyanonaphthalene, 2-cyanonaphthalene, indene, 2-cyanoindene, 1/5-cyanoacenaphthylene, and isomers of cyanopyrene) are orders of magnitude higher than astrophysical models predict, implying that the efficiencies of destruction channels are overestimated, and/or that the efficiencies of molecular formation and stabilization processes are underestimated.

Radiative Stabilization of the Indenyl Cation: Recurrent Fluorescence in a Closed-Shell Polycyclic Aromatic Hydrocarbon, Physical Journal Reviews (open access)

Astrobiology, Astrochemistry,