Isomer-resolved ion-molecule reaction kinetics of HCO+ and HOC+
Year: 2026
Type: article
Abstract: The ̋COp/ŐCp abundance ratio has been observed to vary significantly in different astrophysical environments, making it an important diagnostic tool for exploring the interstellar medium. However, uncertainties in the reaction rates and branching ratios of key chemical reactions involving these ions affect the conclusions drawn from observations of either these species or other species that are derived on their basis. Here, we present isomer-resolved ion-molecule reaction rate coefficients of reactions involving ̋COp and ŐCp using a cryogenic ion trap experiment. We measured the rate coefficients of the isomerization reaction of ŐCp to ̋COp with H2 and , as well as three different reactions producing both isomers: + , + , and + . Our results show that the reaction of predominantly produces ̋COp with a negligible yield of ŐCp. This result is in agreement with recent theoretical predictions, but in major contrast to the generally accepted branching ratio based on previous experimental results. We also find that the isomerization reaction of ŐCp to ̋COp is efficient with both CO CO+ H2 H3+ CO ArH+ CO with H2 H2 and . We were able to assess the impact of our new measured reaction rate coefficients on the predicted ̋COp/ŐCp abundance ratio using a state-of-the-art astrochemical model. CO
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7222938522