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 addi- tion 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 experi- mental 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. Further- more, 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 meteor- itic chemistry are discussed. Subject headings: astrobiology — astrochemistry — ISM: molecules — meteors, meteoroids — molecular processes — ultraviolet: ISM