| After H2, CO and CO2 are amongst the most common molecules in stellar and interstellar environments. Indeed, they are often dominant components in icy mantles of comets and interstellar dust grains. These ice mantles are subject to a varying degree of cosmic radiation, leading to chemical alterations. This thesis presents a study of the IR absorption spectrum (1900--4000 cm-1) of proton-irradiated CO and CO2 thin films. The spectra of the irradiated CO films display several features arising in the vicinity of the CO fundamental which are attributed to carbon oxides such as CnO and C nO2 for n ≤ 7. The formation mechanisms of carbon chains in interstellar environments are of interest since carbon chains (or molecules derived from them) have been considered to be carriers of some of the diffuse interstellar bands. The spectra of UV or proton-irradiated CO 2 films are found to be qualitatively the same and only reveal the formation of CO and CO3. The irradiation of a CO film leaves a residue layer upon the substrate. The spectrum of a subsequent CO sample deposited above this residue presents a very striking example of the Christiansen effect. A Mie calculation is presented which models the resulting perturbation to the spectrum. |
