MOLECULAR UNIVERSE

The physico-chemical models will be coupled to excitation calculations and radiative transfer codes to predict molecular line intensities to be compared with observations. Collisional excitation rates required to compute the line emission come from quantum chemical calculations. The line radiative transfer codes available within the consortium (UPS, U.J.F., RuG, Meudon, Madrid, UMIST, Leiden) are very complementary and treat simultaneously the statistical equilibrium between the level populations and the line transfer in the co-moving frame using accelerated lambda iteration numerical schemes. The models will directly incorporate the new chemical and collisional studies that will be performed within the consortium. Models for photo-dissociation regions (UPS, Leiden, RuG, Meudon) will be applied to surfaces of proto-planetary disks and the inner surfaces of proto-stellar condensations once the protostar turns on. These models will be extended to take into account the propagation of the molecular dissociation front into the surroundings. Models for C-type shocks and for ambipolar diffusion in star forming regions will be extended to include the rates—newly measured in the laboratory or quantum chemically calculated by the consortium—for computation of the ionisation state of interstellar species (molecules, PAHs, carbon clusters and grains) in these environments (Meudon, Durham). Existing chemical models of star forming dark clouds will be updated to focus on chemical evolution driven by ambipolar diffusion and free-fall collapse (UMIST).