2025/06/16 by Jean‐Christophe Loison, Corentin Rossi, Loison, Jean-Christophe +11
Chemistry · Engineering · Physics and Astronomy · #Advanced Chemical Physics Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Molecular Spectroscopy and Structure #Muon and positron interactions and applications
paper · pdf · doi:10.48550/arxiv.2506.13290
openalex publication_date 2025/06/16 · openalex created_date 2025/10/13 · openalex updated_date 2026/07/28
Recent work by Kocheril et al.\citekocheril2025 claimed that phenylium--the cyclic structure of the \ceC6H5+ species--is unreactive toward key interstellar molecules such as molecular hydrogen (\ceH2) and acetylene (\ceC2H2). This finding challenges the previously proposed role of phenylium as a cornerstone in the formation of polycyclic aromatic hydrocarbons (PAHs) \citecherchneff1992,byrne2024. The study focused on the reactivity of \ceC6H5+, formed via the radiative association between \ceC4H3+ and \ceC2H2, believed to be a major pathway for phenylium formation in astrochemical model, e.g. \citebyrne2024. Here, we present new experimental and theoretical evidence that challenges this assumption. Our results demonstrate that phenylium does indeed react with \ceC2H2 under astrophysically relevant conditions. Quantum chemical calculations support this finding by revealing a barrierless mechanism, indicating that the reaction is feasible even in cold interstellar environments. We believe this clarification is critically important, and that further investigations into the formation of the first aromatic ring in space--a process that remains a key bottleneck in our understanding of PAHs formation and growth--is essential.