Chemical Environment and Temperature Effects on the Formation and Destruction of C₃O₂ in Cosmic-Ray-Processed Ices

Astrophysical ices composed of CO and CO₂ undergo complex radiation-driven chemistry, producing reactive species with potential prebiotic relevance. Using the PROCODA kinetic model (642 coupled reactions, 18 tracked species) combined with ion irradiation data, we investigate the main formation and destruction pathways of carbon suboxide (C₃O₂) in CO-, CO₂-, and mixed CO/CO₂-rich ices. A clear two-regime picture emerges. At early fluence, chemistry is matrix-controlled: in pure CO ice, C₃O₂ forms mainly via CO + C₂O → C₃O₂, whereas in pure CO₂ ice it proceeds via CO₂ + C₂O₂ → O₂ + C₃O₂; mixed ices retain CO-involving channels. At chemical equilibrium, routes shift as accumulated intermediates take over: in CO ice, C₃ + CO₂ → C + C₃O₂ dominates, while in CO₂ ice, CO + C₂O₂ → O + C₃O₂ prevails. Destruction is likewise environment-sensitive: C₃O₂ + R → CO + C₂O leads in CO ice, versus C₃O₂ + R → C + C₂O₂ in CO₂ ice (R denotes radiation-induced processes). Raising the temperature from 10 to 20 K enhances bimolecular channels through greater molecular mobility, while leaving radiation-driven pathways largely unaffected. Using C₃O₂ as a prototype, this study provides pathway maps that link composition, temperature, and irradiation history, offering new constraints for astrochemical models and for interpreting JWST and ALMA observations.