Formation of Halogen-bearing Species. II. Irradiation of Chloromethane in Carbon Monoxide Ice with VUV Light and Electrons

The synthesis of chlorine-bearing species in CO ice was studied by the irradiation of CH₃Cl:CO ice at 10 K with vacuum-ultraviolet (VUV) light and energetic electrons. In contrast to the photochemical behavior of CH₃F:CO ice, photolysis of CH₃Cl:CO ice with Lyα or broadband VUV light afforded various products. This discrepancy was attributed to the abundant absorption bands of CH₃Cl in the VUV region, particularly in the Lyα region. The Cl-bearing species including Cl₂O, ClCO, C₃Cl₂, C₃HCl, and HOOCl were characterized by observing their IR features. In contrast, electron bombardment of ice mixtures produced various carbon oxides and primary products, such as CH₂Cl and HCO. In addition, the mechanism of energetic processes in electron bombardment was discussed.