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Astron. Astrophys. 361, 298-302 (2000)

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Infrared spectra of CO2 in H2O:CH3OH:CO2 icy mixtures

M.E. Palumbo and G.A. Baratta

Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy

Received 14 March 2000 / Accepted 20 June 2000


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 12.5 K 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. (2000) this means that these laboratory spectra cannot be directly compared to the astronomical spectra.

Key words: methods: laboratory – ISM: molecules – ISM: dust, extinction – infrared: ISM: lines and bands

Send offprint requests to: M.E. Palumbo (mepalumbo@alpha4.ct.astro.it)

© European Southern Observatory (ESO) 2000

Online publication: September 5, 2000