Year: 2026
Type: article
Abstract: Motivated by the value of CN-bearing molecules as tracers of interstellar physical conditions, we investigate the reactions of adsorbed CN radicals with acetylene and ethylene (C 2 H 2 and C 2 H 4 ) on interstellar dust-grain analogs using quantum chemical calculations. We find that reactivity is strongly controlled by the relative orientation of the reactants. We further show that, on ice, these reactions differ qualitatively from their gas-phase counterparts, stalling at the formation of the adduct complexes C 2 H 2 CN and C 2 H 4 CN and exhibiting newly emerged kinetic barriers for the neutral-radical association. We contextualize our calculations in the same reaction–diffusion framework that would be employed in astrochemical models, finding that, depending on the diffusion energy of the hydrocarbons, these reactions can be either negligible or efficient, highlighting the importance of the local ice structure in interstellar grain chemistry. These findings caution against the use of CN-based tracers that assume barrierless, bimolecular surface reactions involving CN radicals.
Source: The Astrophysical Journal
Authors: Germán Molpeceres, Joan Enrique-Romero
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: Ministerio de Ciencia, Innovación y Universidades, European Commission, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Ministerio de Ciencia e Innovación, HORIZON EUROPE Framework Programme, Consejo Superior de Investigaciones Científicas, European Regional Development Fund, Agencia Estatal de Investigación, European Social Fund
OpenAlex ID: W7154530602