Cold condensation of dust in the ISM
  The condensation of complex silicates with pyroxene and olivine composition
at conditions prevailing in molecular clouds has been experimentally studied.
For this purpose, molecular species comprising refractory elements were forced
to accrete on cold substrates representing the cold surfaces of surviving dust
grains in the interstellar medium. The efficient formation of amorphous and
homogeneous magnesium iron silicates at temperatures of about 12 K has been
monitored by IR spectroscopy. The gaseous precursors of such condensation
processes in the interstellar medium are formed by erosion of dust grains in
supernova shock waves. In the laboratory, we have evaporated glassy silicate
dust analogs and embedded the released species in neon ice matrices that have
been studied spectroscopically to identify the molecular precursors of the
condensing solid silicates. A sound coincidence between the 10 micron band of
the interstellar silicates and the 10 micron band of the low-temperature
siliceous condensates can be noted.
