Surface science investigations of the role of CO₂ in astrophysical ices.

We have recorded reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) data for a range of CO₂-bearing model astrophysical ices adsorbed on a graphitic dust grain analogue surface. Data have been recorded for pure CO₂, for CO₂ adsorbed on top of amorphous solid water, for mixed CO₂:H₂O ices and for CO₂ adsorbed on top of a mixed CH₃OH:H₂O ice. For the TPD data, kinetic parameters for desorption have been determined, and the trapping behaviour of the CO₂ in the H₂O (CH₃OH) ice has been determined. Data of these types are important as they can be used to model desorption in a range of astrophysical environments. RAIR spectra have also shown the interaction of the CO₂ with H₂O and CH₃OH and can be used to compare with astronomical observations, allowing the accurate assignment of spectra.