• Baratta, Giuseppe
• Palumbo, Mariaelisabetta
• Ferini, G.

Abstract

We present a Raman study of pure CH_4, H_2O:CH_4:N_2 and CH_3OH:N_2 frozen films before and after ion irradiation at low (12 K) and high (100 K or 300 K) temperature. By means of Raman spectroscopy, we monitor the structural evolution of each film, whose optical properties are deeply modified by the interaction with the ion beam. Raman spectra show that the sample is partially converted into a refractory residue, which under further irradiation evolves towards an amorphous carbon with a band near 1560 cm<SUP>-1</SUP> (G line) and a shoulder at about 1360 cm<SUP>-1</SUP> (D line). The specific parameters of this 'double-peaked' feature (peaks position, widths and relative intensities) can be used as diagnostic to classify different carbonaceous materials and infer information about their degree of order.We have compared these parameters for our samples (ion irradiated frozen films and residues), for different kinds of hydrogenated carbon grains and for some IDPs. We have found that IDPs have in general a narrower G line, which peaks at higher wavenumbers, than most of the laboratory samples here discussed. This implies that IDPs have a structure with a higher degree of order than that of our samples.Here we present the experimenal results and discuss their relevance to the study of the origin and evolution of IDPs.

Topics

• impedance spectroscopy
• amorphous
• Carbon
• grain
• refractory
• Raman spectroscopy