Radical-assisted polymerisation in interstellar ice analogues: formyl radical and polyoxymethylene

International audienceWe present new laboratory experiments on the low-temperature formation of COMs such as polyoxymethylene (POM), glycolaldehyde (GA), ethylene glycol (EG) and possibly glycer-aldehyde (GCA) and glycerol (GCO) through radical-induced reactivity from VUV photolysis of formaldehyde in Ar and Xe matrices. The radical reactivity and the endogenous formation of COMs were monitored in-situ via infrared spectroscopy in the solid state and post photol-ysis with temperature programmed desorption (TPD) using a quadripole mass spectrometer. Based on experimental finding and quantum calculations, we elaborate a formation pathway for formaldehyde polymerisation induced by radicals (HCO and CH 2 OH) that support the POM formation in cometary environments. In addition, fragmentation patterns obtained from the sublimation of short chain-length POM are consistent with data collected by the Ptolemy instrument on-board the Rosetta mission and strengthen the POM identification made by this instrument