Volume 593, September 2016
|Number of page(s)||9|
|Section||Atomic, molecular, and nuclear data|
|Published online||21 September 2016|
Radical-induced chemistry from VUV photolysis of interstellar ice analogues containing formaldehyde
PIIM, UMR 7345, Aix-Marseille Université, Avenue Escadrille Normandie-Niemen, 13397 Marseille, France
Received: 5 February 2016
Accepted: 16 June 2016
Surface processes and radical chemistry within interstellar ices are increasingly suspected to play an important role in the formation of complex organic molecules (COMs) observed in several astrophysical regions and cometary environments. We present new laboratory experiments on the low-temperature solid state formation of complex organic molecules – glycolaldehyde, ethylene glycol, and polyoxymethylene – through radical-induced reactivity from VUV photolysis of formaldehyde in water-free and water-dominated ices. Radical reactivity and endogenous formation of COMs were monitored in situ via infrared spectroscopy in the solid state and post photolysis with temperature programmed desorption (TPD) using a quadripole mass spectrometer. We show the ability of free radicals to be stored when formed at low temperature in water-dominated ices, and to react with other radicals or on double bonds of unsaturated molecules when the temperature increases. It experimentally confirms the role of thermal diffusion in radical reactivity. We propose a new pathway for formaldehyde polymerisation induced by HCO radicals that might explain some observations made by the Ptolemy instrument on board the Rosetta lander Philae. In addition, our results seem to indicate that H-atom additions on H2CO proceed preferentially through CH2OH intermediate radicals rather than the CH3O radical.
Key words: astrochemistry / molecular data / methods: laboratory: solid state / ISM: molecules
© ESO, 2016
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.