URSO, Riccardo GiovanniRiccardo GiovanniURSOHénault, E.E.HénaultBrunetto, R.R.BrunettoBaklouti, D.D.BakloutiBARATTA, GiuseppeGiuseppeBARATTADjouadi, Z.Z.DjouadiElsaesser, A.A.ElsaesserSCIRE` SCAPPUZZO, CarlottaCarlottaSCIRE` SCAPPUZZOSTRAZZULLA, GiovanniGiovanniSTRAZZULLAPALUMBO, Maria ElisabettaMaria ElisabettaPALUMBO2023-07-252023-07-2520220004-6361http://hdl.handle.net/20.500.12386/34340Context. Cosmic rays and solar energetic particles induce changes in the composition of compounds frozen onto dust grains in the interstellar medium (ISM), in comets, and on the surfaces of atmosphere-less small bodies in the outer Solar System. This induces the destruction of pristine compounds and triggers the formation of various species, including the precursors of complex organics. <BR /> Aims: We investigate the role of energetic ions in the formation of formaldehyde (H<SUB>2</SUB>CO) and acetaldehyde (CH<SUB>3</SUB>CHO), which are observed in the ISM and in comets, and which are thought to be the precursors of more complex compounds such as hexamethylenete-tramine (HMT), which is found in carbonaceous chondrites and in laboratory samples produced after the irradiation and warm-up of astrophysical ices. <BR /> Methods: We performed ion irradiation of water, methanol, and ammonia mixtures at 14-18 K. We bombarded frozen films with 40-200 keV H<SUP>+</SUP> that simulate solar energetic particles and low-energy cosmic rays. Samples were analysed by infrared transmission spectroscopy. <BR /> Results: Among other molecules, we observe the formation of H<SUB>2</SUB>CO and CH<SUB>3</SUB>CHO, and we find that their abundance depends on the dose and on the stoichiometry of the mixtures. We find that the H<SUB>2</SUB>CO abundance reaches the highest value after a dose of 10 eV/16u and then it decreases as the dose increases. <BR /> Conclusions: The data suggest that surfaces exposed to high doses are depleted in H<SUB>2</SUB>CO. This explains why the amount of HMT in organic residues and that formed after irradiation of ices depends on the dose deposited in the ice. Because the H<SUB>2</SUB>CO abundance decreases at doses higher than 10 eV/16u, a lower quantity of H<SUB>2</SUB>CO is available to form HMT during the subsequent warm-up. The H<SUB>2</SUB>CO abundances caused by ion bombardment are insufficient to explain the ISM abundances, but ion bombardment can account for the abundance of CH<SUB>3</SUB>CHO towards the ISM and comets.STAMPAenArticle10.1051/0004-6361/2022445222-s2.0-85145358847https://www.aanda.org/articles/aa/full_html/2022/12/aa44522-22/aa44522-22.htmlhttps://api.elsevier.com/content/abstract/scopus_id/851453588472022A&A...668A.169UFIS/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