A variety of observations have shown that surprisingly complex molecules are an important component of the interstellar medium. Molecules have an important influence on the heating and cooling of interstellar gas and, therefore, on the cloud structure of the interstellar medium in galaxies. Molecular clouds are the (only) site of ongoing star formation to a large extent because molecules are efficient gas coolers, thereby diminishing thermal support relative to self-gravity. In addition, molecules suppress the degree of ionization in these clouds and therefore "decouple" the gas from any supporting magnetic fields.
Over the next five years, international ground based and space-based missions will open the universe to high spatial and spectral resolution studies at infrared and millimeter wavelengths. This will allow to study, in much greater details, the composition and evolution of molecules in space.
These new missions can be expected to lead to the detection of many new spectral features.
Identificati on, analysis and interpretation of these features in terms of the physical and chemical characteristics of the astronomical sources require detailed astronomical modeling supported by laboratory measurements and theoretical studies of chemical reactions and collisional excitation rates of species of astrophysical relevance.
I will focus on the following aspects of this highly interdisciplinary research area :
- identification in relation with spectroscopic measurements and theoretical quantum chemistry
- collisional excitation rates with the predominant collision partners (atomic and molecular hydrogen, helium, electrons)
- balance between formation and destruction processes under astrophysically relevant conditions (eg., low temperature, low pressure)
The need for adapted data basis will be emphasized.
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