Formation pathways of complex organic molecules: OH^• projectile colliding with methanol ice mantle (CH₃OH)₁₀

¹ Universidad Autónoma de Chile, Facultad de Ingeniería, Núcleo de Astroquímica & Astrofísica, Av. Pedro de Valdivia 425, Providencia, Santiago, Chile
e-mail: natalia.inostroza@uautonoma.cl
² Universidad de Chile, Facultad de Ciencias Físicas y Matemáticas, Departamento de Astronomía, Camino el observatorio 1515, Las condes, Santiago, Chile

Received: 6 March 2020
Accepted: 12 June 2020

Abstract

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 10–22 eV, 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.