RT Journal Article
SR Electronic
T1 Isomer-specific kinetics of the C<sup>+</sup> + H<sub>2</sub>O reaction at the temperature of interstellar clouds
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP eabe4080
DO 10.1126/sciadv.abe4080
VO 7
IS 2
A1 Yang, Tiangang
A1 Li, Anyang
A1 Chen, Gary K.
A1 Yao, Qian
A1 Suits, Arthur G.
A1 Guo, Hua
A1 Hudson, Eric R.
A1 Campbell, Wesley C.
YR 2021
UL http://advances.sciencemag.org/content/7/2/eabe4080.abstract
AB The reaction C+ + H2O → HCO+/HOC+ + H is one of the most important astrophysical sources of HOC+ ions, considered a marker for interstellar molecular clouds exposed to intense ultraviolet or x-ray radiation. Despite much study, there is no consensus on rate constants for formation of the formyl ion isomers in this reaction. This is largely due to difficulties in laboratory study of ion-molecule reactions under relevant conditions. Here, we use a novel experimental platform combining a cryogenic buffer-gas beam with an integrated, laser-cooled ion trap and high-resolution time-of-flight mass spectrometer to probe this reaction at the temperature of cold interstellar clouds. We report a reaction rate constant of k = 7.7(6) × 10−9 cm3 s−1 and a branching ratio of formation η = HOC+/HCO+ = 2.1(4). Theoretical calculations suggest that this branching ratio is due to the predominant formation of HOC+ followed by isomerization of products with internal energy over the isomerization barrier.