Experimental evidence for Glycolaldehyde and Ethylene Glycol formation by surface hydrogenation of CO molecules under dense molecular cloud conditions
  This study focuses on the formation of two molecules of astrobiological
importance - glycolaldehyde (HC(O)CH2OH) and ethylene glycol (H2C(OH)CH2OH) -
by surface hydrogenation of CO molecules. Our experiments aim at simulating the
CO freeze-out stage in interstellar dark cloud regions, well before thermal and
energetic processing become dominant. It is shown that along with the formation
of H2CO and CH3OH - two well established products of CO hydrogenation - also
molecules with more than one carbon atom form. The key step in this process is
believed to be the recombination of two HCO radicals followed by the formation
of a C-C bond. The experimentally established reaction pathways are implemented
into a continuous-time random-walk Monte Carlo model, previously used to model
the formation of CH3OH on astrochemical time-scales, to study their impact on
the solid-state abundances in dense interstellar clouds of glycolaldehyde and
ethylene glycol.
