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.