Side Group Addition to the Polycyclic Aromatic Hydrocarbon Coronene by Ultraviolet Photolysis in Cosmic Ice Analogs

Ultraviolet photolysis of various coronene-ice mixtures at low temperature and pressure caused the addition of amino (”NH2), methyl (”CH3), methoxy (”OCH3), cyano/isocyano (”CN, ”NC), and acid (”COOH) functional groups to the polycyclic aromatic hydrocarbon (PAH) coronene (C24H12), in addition to previously reported alcohol (”OH) and ketone (>C»O) formation. This work represents the first experimental evidence that ice photochemistry may have contributed to the aromatics bearing carbon and nitrogen containing side groups that are detected in primitive meteorites and interplanetary dust particles. Furthermore, these results suggest that a wide range of modified PAHs should be expected in interstellar ices and materials that predated solar system formation. The implications of these results for interstellar and meteoritic chemistry are discussed. Subject headings: astrobiology — astrochemistry — ISM: molecules — meteors, meteoroids — molecular processes — ultraviolet: ISM