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

TL;DR

This study explores how cosmic rays and temperature affect the formation and breakdown of C3O2 in icy environments in space.

Contribution

The paper provides detailed pathway maps linking ice composition, temperature, and irradiation history for C3O2 chemistry.

Findings

C3O2 forms via different pathways in pure CO and CO2 ices.

Temperature increases from 10 to 20 K enhance bimolecular reactions but not radiation-driven ones.

Destruction of C3O2 depends on the ice composition and radiation processes.

Abstract

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.

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