This proposal is devoted to the study of interaction between the gas
and the solid phases in dense molecular clouds. In addition we wish
to detect weak solid state features that will help to establish a link
between observations and our laboratory simulations. Preliminary results
of our ISO proposals (MMDUSTY1 and SOLSTA) have clearly shown that, in
the line of sight of embedded protostars, molecular ices made of simple
molecules (H2O, CO, CO2, CH4) are easily detected.
Superimposed to the broad solid state features, gas phase lines of the
same molecules (especially H2O and CO2) have been observed.
Revisiting our goals, we propose, using SWS AOT6 in some well defined
ranges to obtain spectra of the cold molecular foreground in the line
of sight of a protostar. These ranges fall in the rotation-vibration lines
of H2O, CO, CO2 and CH4. We have also selected a few ranges pertaining
to new solid state features in the 30-45 micron range seen in two of
our objects.
The ultimate goal is to understand the role of grains in the chemistry of
molecular clouds and gain some insight in the mineral composition of the
silicate cores of the grains.