Mechanistical studies on the formation and destruction of carbon monoxide (CO), carbon dioxide (CO2), and carbon trioxide (CO3) in interstellar ice analog samples

Abstract

A series of ice mixtures containing carbon monoxide (CO), carbon dioxide (CO₂), and molecular oxygen (O₂) with varying carbon-to-oxygen ratios from 1 ∶ 1.5 to 1 ∶ 4 were irradiated at 10 K with energetic electrons to derive formation mechanisms and destruction pathways of carbon monoxide (CO), carbon dioxide (CO₂), and carbon trioxide (CO₃) in extraterrestrial, low temperature ices. Reactants and products were analyzed on line and in situ via absorption–reflection–absorption FTIR spectroscopy in the solid state, while the gas phase was sampled by a quadrupole mass spectrometer (QMS). Additionally, isotopically mixed ices consisting of (i) ¹³CO ∶ C¹⁸O ∶ CO₂, (ii) CO₂ ∶ C¹⁸O₂, and (iii) CO₂ ∶ ¹⁸O₂ were irradiated in order to derive mechanistical and kinetic information on the production and destruction pathways of the following species: (i) ¹³CO, C¹⁸O, CO₂, CO, ¹³CO₂, ¹⁸OCO, and ¹³CO₃ (C_2v), (ii) CO₂, C¹⁸O₂, CO, C¹⁸O, ¹⁸OCO, CO₃ (C_2v), OC¹⁸OO (C_2v), OC¹⁸O₂ (C_2v), ¹⁸OCO₂ (C_2v), ¹⁸OC¹⁸OO (C_2v), and C¹⁸O₃ (C_2v), and (iii) CO₂, CO, ¹⁸OCO, C¹⁸O, and C¹⁸O₂.