Chuang, K. -J.K. -J.ChuangFEDOSEEV, GLEBGLEBFEDOSEEVQasim,D.QasimIoppolo, S.S.IoppoloJäger, C.C.JägerHenning, Th.Th.HenningPALUMBO, Maria ElisabettaMaria ElisabettaPALUMBODishoeck, E. F. vanE. F. vanDishoeckLinnartz, H.H.Linnartz2022-01-242022-01-2420200004-6361http://hdl.handle.net/20.500.12386/31348Complex organic molecules (COMs) have been identified toward high- and low-mass protostars as well as molecular clouds, suggesting that these interstellar species originate from the early stage(s) of starformation. The reaction pathways resulting in COMs described by the formula C$_2$H$_\text{n}$O are still under debate. In this work, we investigate the laboratory possible solid-state reactions that involve simple hydrocarbons and OH-radicals along with H$_2$O ice under translucent cloud conditions (1$\leq$A$_V$$\leq$5 and \textit{n}$_\text{H}$$\sim$10$^3$ cm$^{-3}$). We focus on the interactions of C$_2$H$_2$ with H-atoms and OH-radicals, which are produced along the H$_2$O formation sequence on grain surfaces at 10 K. Ultra-high vacuum (UHV) experiments were performed to study the surface chemistry observed during C$_2$H$_2$ + O$_2$ + H codeposition, where O$_2$ was used for the in-situ generation of OH-radicals. Reflection absorption infrared spectroscopy (RAIRS) was applied to in situ monitor the initial and newly formed species. After that, a temperature-programmed desorption experiment combined with a Quadrupole mass spectrometer (TPD-QMS) was used as a complementary analytical tool. The investigated 10 K surface chemistry of C$_2$H$_2$ with H-atoms and OH-radicals not only results in semi and fully saturated hydrocarbons, such as ethylene (C$_2$H$_4$) and ethane (C$_2$H$_6$), but it also leads to the formation of COMs, such as vinyl alcohol, acetaldehyde, ketene, ethanol, and possibly acetic acid. It is concluded that OH-radical addition reactions to C$_2$H$_2$, acting as a molecular backbone, followed by isomerization (i.e., keto-enol tautomerization) via an intermolecular pathway and successive hydrogenation provides a so far experimentally unreported solid-state route for the formation of these species without the need of energetic input. The kinetics of acetaldehyde reacting with impacting H-atoms leading to ketene and ethanol is found to have a preference for the saturated product. The astronomical relevance of the reaction network introduced here is discussed.STAMPAenArticle10.1051/0004-6361/2019373022-s2.0-85083236686WOS:000524541200001https://www.aanda.org/articles/aa/full_html/2020/03/aa37302-19/aa37302-19.htmlhttp://arxiv.org/abs/2002.06971v12020IAUS..350...77PFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation