UV irradiation of polycyclic aromatic hydrocarbons in ices: Production of alcohols, quinones, and ethers

Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultrav iolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones; and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These cl asses of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may e xplain the deuterium enrichments found in certain meteoritic molecules. Thi s work has important implications for extraterrestrial organics in biogenes is.