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Astron. Astrophys. 321, 618-624 (1997)

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Is it possible to detect frozen O2 and N2 on interstellar grains?

G. Strazzulla 1, J.R. Brucato 2, M.E. Palumbo 1 and M.A. Satorre 3

1 Osservatorio Astrofisico di Catania, Città Universitaria, I-95125 Catania, Italy
2 Istituto di Astronomia, Università di Catania, Città Universitaria, I-95125 Catania, Italy
3 Departament Fisica Aplicada EPSA (UPV), Escola Politecnica Superior Alcoi, Alicante, Spain

Received 13 May 1996 / Accepted 8 October 1996


We continue to study the effects of ion irradiation on frozen ices with a view to their astrophysical relevance. The technique used to evidence molecular alteration is "in situ" infrared (IR) spectroscopy. Here, we present results obtained irradiating by 3-60 keV helium and argon ions, frozen CO, and mixtures CO:O2 and CO:N2. The relevance of these studies for astrophysical applications is related to the fact that IR bands of frozen O2 and N2 are difficult to be observed. We investigate if their presence on ice mantles of interstellar grains could be evidenced through the changes in the CO profile or the presence of new species formed by energetic processing. The results indicate that the CO band at around 2140 cm-1 is only slightly modified by the simple mixing with the two non-polar species and, more deeply, by ion irradiation of the mixtures. Carbon dioxide (CO2) is the major species produced by irradiation. In CO:O2 mixtures ozone (O3) is produced at a large rate. Also carbon suboxides are formed by ion irradiation of CO and CO:N2 mixtures, the profile of their bands is different in the two cases and can be used as tracer of the presence of N2 in icy mantles.

Key words: ISM: dust – ISM: molecules – infrared: interstellar: lines

Send offprint requests to: G. Strazzulla

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998