INFRARED-SPECTRA AND NATURE OF THE PRINCIPAL CO TRAPPING SITES IN AMORPHOUS AND CRYSTALLINE H2O ICE

A detailed experimental study of the infrared characteristics of CO in H2O ice matrixes (10-150 K) has been performed. The effects of therma l and ion irradiation processes have also been examined. H2O:CO ice mi xtures have been obtained both by co-deposition of H2O and CO (at 10 I t) and by diffusion (at similar to 27 K) of eo into a preformed water ice him. It has been confirmed that CO does not diffuse into the ice a t temperatures below similar to 26 K. Results have been compared with previously reported diffusion experiments at 42 K. Laboratory experime nts show that the profile (shape, width, and peak position) of the CO band depends on the structure of the water matrix it is embedded in an d on the process (co-deposit or diffusion) by which the mixture has be en obtained. This is attributed to Be different amount of energy invol ved in the process which forms the mixture. These studies are importan t to understand the physical and chemical properties of ices. Furtherm ore information on the history of molecular ices in astrophysical envi ronments are obtained comparing observed spectra with those taken in l aboratory.