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Harvard ADS: Proposed importance of HOCO chemistry: Inefficient formation of CO_2 from CO and OH reactions on ice dust

Paper abstract: With the advent of JWST ice observations, dedicated studies on the formation reactions of detected molecules are becoming increasingly important. One of the most interesting molecules in interstellar ice is CO_2. Despite its simplicity, the main formation reaction considered, CO + OH -> CO_2 + H through the energetic HOCO* intermediate on ice dust, is subject to uncertainty because it directly competes with the stabilization of HOCO as a final product which is formed through energy dissipation of HOCO* to the water ice. When energy dissipation to the surface is effective during reaction, HOCO can be a dominant product. In this study, we experimentally demonstrate that the major product of the reaction is indeed not CO_2, but rather the highly reactive radical HOCO. The HOCO radical can later evolve into CO_2 through H-abstraction reactions, but these reactions compete with addition reactions, leading to the formation of carboxylic acids (R-COOH). Our results highlight the importance of HOCO chemistry and encourage further exploration of the chemistry of this radical.