UV Irradiation of Polycyclic Aromatic Hydrocarbons in Ices: Production of Alcohols, Quinones

Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultra-violet (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 classes of compounds are all present in carbonaceous meteorites. Hydrogen and deu-terium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis. Infrared (IR) spectroscopy of the interstellar medium (ISM), combined with laboratory stud-ies of realistic interstellar analog materials, is a powerful means for identifying the matter that exists between the stars. The ISM is known t