2020A&A...641A..14I

In this article, we simulated the collisions of an OH^* projectile impacting on a methanol cluster formed by ten units of methanol to mimic an ice mantle (CH₃OH)₁₀. The chemical processes occurring after the impact were studied through Born-Oppenheimer (ab-initio) molecular dynamics. We focus on collisions with initial kinetic impact energy of 10-22eV, where the richest chemistry happens. We report the formation mechanisms of stable complex organic molecules (COMs) such as methoxymethanol CH₃OCH₂OH, formic acid HCOOH, formyl radical HCO, formaldehyde H₂CO and its elusive HCOH isomer. We show that CH₂(OH)₂, ^*CH₂OH or ⁺CH₂OH are key intermediates to generate H₂CO and other COMs. We compare the outcomes using OH^* with those using OH^– projectiles. These processes are likely relevant to the production of COMs in astrophysical environments. We discuss its formation mechanism and the astrophysical implications of these chemical pathways in star-forming regions.