Formation of Molecular Hydrogen on Amorphous Water Ice: Influence of Morphology and Ultraviolet Exposure

Abstract

In the past five years we have conducted laboratory studies of the formation of key molecules on dust grain analogues in astrophysically relevant conditions. Here we report on: 1) The formation of molecular hydrogen on different types of amorphous water ice. We show that mass spectra of desorbing molecular hydrogen upon formation are sensitive to the way in which ice is deposited on a cold substrate, to its thermal history, and to the action of UV photons. Implications that these results bear on H2 formation in dense quiescent clouds are presented and discussed; and 2) The oxidation of carbon monoxide. The formation of C O2 has been studied by the reaction C Osurf ace + OgasC O2 . Implications for the formation of C O2 in quiescent clouds are discussed.