VIBRATIONAL SPECTROSCOPY OF ION-IRRADIATED FROZEN BUTANE

In this paper we present a detailed experimental study of the evolutio n of frozen butane (10 K) before, during and after irradiation with 3 keV He ion beams. Because of irradiation, different molecular species are formed, among which a refractory organic material that, upon furth er irradiation, evolves towards an amorphous carbon. The techniques us ed for the analysis are ''in situ'' infrared (IR) and Raman spectrosco py. The results may have relevance in astrophysics: the produced refra ctory residues are in fact good analogs of the organic mantles on inte rstellar grains and of the organics found in carbonaceous meteorites s uch as Orgueil and Murchison.