ION IRRADIATION OF ASTROPHYSICAL ICES

We report recent experimental studies on the physical-chemical effects induced by fast ions colliding with frozen gases (CO, CH3 OH, Ch(4), CO2) and mixtures with water simulating icy targets in space (frosts o n external planets and satellites, comets and interstellar ices). We h ave studied, by IR spectroscopy, the formation of new molecules, the a lteration of band profile, the spectral changes of the original compou nds and the formation of an organic refractory residue left over after ion irradiation. In particular, we present here the results of the me asurements of the CO/CO2 ratio resulting from the irradiation of sever al ice mixtures.