LABORATORY EVIDENCE FOR EFFICIENT WATER FORMATION IN INTERSTELLAR ICES

摘要: Even though water is the main constituent in interstellar icy mantles, its chemical origin not well understood. Three different formation routes have been proposed following hydrogenation of O, O2 ,o r O3 on grains, but experimental evidence largely lacking. We present a solid state astrochemical laboratory study which one these tested. For this purpose ice bombarded by H or D atoms under ultrahigh vacuum conditions at astronomically relevant temperatures ranging from 12 to 28 K. The use reflection absorption infrared spectroscopy (RAIRS)permitsderivationof reactionratesandshowsefficientformationof H2O(D2O)witharatethatissurprisingly independent temperature. This route converts into H2O via H2O2 and found be orders magnitude more efficient than previously assumed. It should therefore considered as an important channel for illustrated model calculations. Subject headingg astrochemistry — infrared: ISM ISM: molecules methods: Online material: color figures