Effect of chemical composition on the neutral reaction products produced during electron beam irradiation of carbon tetrachloride/water (ice) films

Abstract

The neutral reaction products formed during electron beam irradiation of carbon tetrachloride/water (ice) films have been studied as a function of the film's initial CCl₄ ∶ H₂O ratio using a combination of reflection absorption infrared spectroscopy, mass spectrometry and X-ray photoelectron spectroscopy. When the initial CCl₄ ∶ H₂O ratio was high, the dominant reaction products in the film were C₂Cl₄ and a partially chlorinated carbonaceous film (CCl_x) formed as the result of carbon–carbon coupling reactions in the film. In these CCl₄ rich films, chlorine is partitioned mainly into the gas phase while CO is the dominant carbon-containing gas phase species. As the CCl₄ ∶ H₂O ratio decreases, CO₂ becomes an increasingly important reaction product at the expense of species generated from carbon–carbon coupling reactions, while chlorine is increasingly partitioned as HCl in the film, producing H₃O⁺ and Cl⁻. The production of both H₂ and O₂ from electron stimulated reactions associated with H₂O are suppressed in CCl₄/H₂O films, although oxygen is more efficiently quenched in the presence of CCl₄.