Time: 11:00 h
Author: Ko-Ju Chuang
Large areas of space are filled by molecular clouds that consist of gas and
(sub)-micron sized silicate and carbonaceous dust grains that are the
remnants of dead stars. When these clouds start gravitationally collapsing,
the decreasing temperature and increasing density cause gas particles to
start accreting onto dust grain surfaces that act as highly effective
cryopumps. This results in layered geometries of partially mixed ices on
top of the grains that act as molecule reservoirs and cryogenic catalysts
on which both simple and complex molecules form in surface reactions,
triggered by impacting atoms, electrons and cosmic rays or irradiation by
vacuum UV light. These grains form the material from which celestial bodies
–comets and planets and their moons –form. A good understanding of the
elementary processes taking place in dark interstellar clouds, therefore,
is necessary to understand the chemical inventory of stellar systems, like
our own Solar system.
This talk focuses on laboratory studies investigating the surface
chemistry of CO-rich ices on dust grains at temperatures as low as 10 K.
The formation mechanisms of complex organic molecules (COMs) are
investigated by non-energetic processes (e.g., hydrogenation) and energetic
processes (e.g., photolysis). Moreover, the net transfer of the newly
formed hydrogenated species from grain surfaces into the gas phase through
non-thermal desorption is investigated to link the detection of COMs in the
gas phase to their formation in the solid state.