On the synthesis of N-O bearing species in astrophysical ices - an infrared spectroscopic study using heavy-ion irradiation of solid N-2:CO samples

The interstellar chemistry of nitrogen is considerably less understood than the chemistry of other common elements, such as carbon and oxygen. Even though a relatively large number of species containing nitrogen atoms have already been detected in the interstellar medium, only six of them bear a nitrogen-oxygen (N-O) bond. Some astrophysical and primeval Earth models suggest that N-O species, such as hydroxylamine (NH2OH), are potential precursors of prebiotic amino acids, and even peptides. In this work, we have analyzed an apolar ice mixture of N-2:CO of astrophysical interest to investigate possible formation mechanisms of N-O bearing molecules due to processing of the sample by Ni-64(24)+ 538 MeV ions (8.4 MeV/u) at 14 K. The results show the formation of simple nitrogen oxides (N1-2Oy), but no CN-O species of any kind. We have also determined the formation cross-sections of some of the products, as well as the destruction cross-sections of precursors and products. The results presented here are discussed in light of our previous work on the processing of a NH3:CO ice mixture, which have found no N-O bearing molecules at all.