Vibrational spectroscopy of ion-irradiated ices.

In the last 20 years we have studied some effects induced by fast ions (E approximately keV-MeV) impinging on solid materials (mainly ices) with a view to their astrophysical relevance. The main techniques used have been infrared and Raman spectroscopy. Here we review some of the results obtained so far concerning, in particular, the formation of new species not present in the original sample. When hydrocarbons are an important constituent of the target ion irradiation gives rise also to a refractory residue which is left over after warming up. In addition we present some preliminary results of a new study, still in progress, on the infrared properties of the organic residue formed after irradiation of an icy mixture with H-, C-, N- and O-bearing species. Furthermore we present the micro-Raman spectra of some fragments of Orgueil a carbonaceous chondrite meteorite. Some astrophysical applications of these laboratory results are also discussed.