28-30 September 2016
Tagungstätte Schloss Ringberg, Kreuth
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First Measurements of the Rate Coefficients for the Reactions of OH+ and H2O+ with H2 below 100 K


  • Dr. Sunil Kumar SUDHAKARAN

Primary authors



One of the unsolved puzzles in astrochemistry is the surprisingly high abundance of the ionized water molecule (H$_2$O$^+$) in the interstellar medium. The high abundance is unexpected because the measured reaction rate coefficients of H$_2$O$^+$ with H$_2$ [1] (6.6 x 10$^{-10}$ cm$^{-3}$ s$^{-1}$, a relatively high value) suggest that the ubiquitous H$_2$ in space will readily react with it to form H$_3$O$^+$. However no measurements of the reaction rate coefficients have been reported below 100 K, the temperature range relevant for the interstellar medium. In this contribution, we present the first results of the measurements of the rate coefficients below 100 K for the reactions of OH$^+$ and H$_2$O$^+$ with molecular hydrogen, two of the important gas-phase astrochemical reactions proposed to be responsible for the formation of water in space. Preliminary data indicate that the rate of reaction of H$_2$O$^+$ with H$_2$ proceeds at a higher rate than at room temperature in contrast to the trend observed from the previous measurements [1].


  1. Martinez, O., Jr et al. Temperature-dependent kinetic measurements and quasi-classical trajectory studies for the OH(+) + H2/D2 → H2O(+)/HDO(+) + H/D reactions. J. Chem. Phys. 143, 114310 (2015).