An experimental investigation of the effects of irradiation on carbon- and oxygen-bearing species in interstellar ices

Understanding the irradiation effects on interstellar ices is important for several reasons. It can help us understand the chemical inventory of the primordial ices which formed our solar system. The chemical diversity of these ices is reflected in the composition of the icy bodies they evolve into; including comets, Kuiper Belt Objects, and interplanetary dust particles. Each of these represents a source of water as well as biologically important precursors that could potentially seed the Earth. The molecules which are constituents of these ices are relatively simple chemical species. However, during the long lifetimes of interstellar clouds they are subjected to radiation from Galactic Cosmic Rays, as well as UV radiation from young stellar objects. This radiation induces the formation of new chemical species, as evidenced by the complex chemical species which are detected within hot molecular cores. Here, as new stars begin to form, they heat up surrounding icy grains, causing them to sublime and release the newly formed species. This research is focused on the effects of irradiation on carbon- and oxygen- bearing species using keV electrons, which simulate the effects of secondary electrons produced within the track of cosmic rays. Since the effects of irradiation on pure carbon monoxide and pure carbon dioxide results in the generation of vastly different species; the former generates linear chain species, whereas the latter forms predominantly carbon oxide species. In order to understand the underlying processing, a range of irradiation experiments on carbon oxide ices were conducted where the ratio of C:0 varies from 1 .5: 1 to 1:4.