Reactive Desorption and Radiative Association as Possible Drivers of
  Complex Molecule Formation in the Cold Interstellar Medium
  The recent discovery of terrestrial-type organic species such as methyl
formate and dimethyl ether in the cold interstellar gas has proved that the
formation of organic matter in the Galaxy begins at a much earlier stage of
star formation than was thought before. This discovery represents a challenge
for astrochemical modelers. The abundances of these molecules cannot be
explained by the previously developed "warm-up" scenario, in which organic
molecules are formed via diffusive chemistry on surfaces of interstellar grains
starting at 30 K, and then released to the gas at higher temperatures during
later stages of star formation. In this article, we investigate an alternative
scenario in which complex organic species are formed via a sequence of
gas-phase reactions between precursor species formed on grain surfaces and then
ejected into the gas via efficient reactive desorption, a process in which
non-thermal desorption occurs as a result of conversion of the exothermicity of
chemical reactions into the ejection of products from the surface. The proposed
scenario leads to reasonable if somewhat mixed results at temperatures as low
as 10 K and may be considered as a step towards the explanation of abundances
of terrestrial-like organic species observed during the earliest stages of star
formation.
