VUV photopolymerization of ketene under interstellar conditions: from the dilute phase to the condensed phase

Abstract

ABSTRACT 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.