2022MNRAS.514.3754I

The photodecomposition of ketene under interstellar conditions and how the resulting photofragments may recombine in the 3-300 K temperature range could play an important role in investigations related to astrochemistry and astrobiology. Using a combination of bulk ice and rare-gas matrix isolation studies coupled to Fourier transform infrared (FTIR) spectroscopy, this work aims to understand the vacuum ultraviolet (VUV) photochemistry of CH₂CO in solid phase to mimic the photochemistry of organic species trapped in the icy interstellar grains. We show that the photolysis of CH₂CO depends strongly on the environments where it is trapped. The VUV photolysis of CH₂CO/Ne in dilute phase leads to kinetically stable and unstable species such as CO, C₂H₂, CH₄, C₂H₄, C₂H₆, H₂CO, CH₃CHO, HCCO, C₂O, C₃O, and C₄O. However, the same experiment carried out in condensed phase shows that the photolysis of CH₂CO ice produces mainly an organic residue, which is directly observed at 10 K and remains stable in solid phase at 300 K. The infrared (IR) spectroscopy analysis suggests that the resulting organic residue could be a polyketone formed at 10 K through the VUV photopolymerization of ketene.