Mechanistical studies on the formation of carbon dioxide in extraterrestrial carbon monoxide ice analog samples

Abstract

Binary ice mixtures of two carbon monoxide isotopomers, ¹³C¹⁶O and ¹²C¹⁸O, were subjected at 10 K to energetic electrons to investigate the interaction of ionizing radiation with extraterrestrial, carbon monoxide bearing ices. The chemical modifications were monitored on line and in situ via absorption–reflection–absorption Fourier transform infrared spectroscopy as well as in the gas-phase via a quadrupole mass spectrometer. Detected products include two newly formed carbon monoxide isotopomers (¹²C¹⁶O and ¹³C¹⁸O), carbon dioxide (¹²C¹⁶O₂, ¹²C¹⁸O¹⁶O, ¹²C¹⁸O₂, ¹³C¹⁶O₂, ¹³C¹⁸O¹⁶O, and ¹³C¹⁸O₂), and dicarbon monoxide (¹²C¹³C¹⁶O and ¹³C¹³C¹⁶O). Kinetic profiles of carbon monoxide and of carbon dioxide were extracted and fit to derive reaction mechanisms and information on the decomposition of carbon monoxide and on the formation of carbon dioxide in extraterrestrial ice analog samples.