2000A&A...361..298P

We have studied by laboratory infrared spectroscopy the profile of the CO₂ absorption bands in different H₂O:CH₃OH:CO₂ mixtures. Icy mixtures have been accreted on a substrate at 12.5K inclined of 45 degrees with respect to the infrared beam of the spectrometer. Spectra have been taken with the electric vector of the infrared beam parallel (P polarized) and perpendicular (S polarized) to the plane of incidence. The samples have been warmed up and spectra have been taken at different temperatures. We confirm CO₂ segregation after warm-up. Furthermore we find that when segregation occurs the profile of CO₂ bands are different in the two different polarization cases. As shown by Baratta et al. (2000A&A...357.1045B) this means that these laboratory spectra cannot be directly compared to the astronomical spectra.