Temperature dependence of two key interstellar reactions of H 3+: O(3P) + H3+ and CO+ H3+

Stephen J. Klippenstein, Yuri Georgievskii, Benjamin J. McCall

Research output: Contribution to journalArticle


The reactions of H3+ with CO and with O( 3P) are the two most important reactions for the destruction of H3+ in dense interstellar clouds. These two reactions are studied with sophisticated theoretical methods that should provide accurate predictions for the rate coefficients. The potential energy surfaces are studied with high- level electronic structure methods. For both reactions, simple long-range expansions are shown to be sufficiently accurate for predicting the kinetics at room temperature and lower. The kinetics is predicted from a combination of transition state theory, trajectory simulations, and master equation analysis. For the O(3P) reaction, the interplay between the spin-orbit and the charge-quadrupole interactions is explicitly considered. For the CO reaction, we also consider the isomerization and decomposition dynamics of the two initially formed adducts. The final predictions, which are expected to be accurate to about 10 to 20%, are compared with the available experimental data. For the O(3P) reaction, the predicted rate coefficient is accurately reproduced by the expression 1.14 × 10-9 (T/300)-0.156 exp( - 1.41/T)cm3 molecule-1 s-1 over the 5 to 400 K temperature range. For the CO reaction, the predicted rate coefficients for the H2 + HCO+ and H2 + HOC+ channels are accurately reproduced by the expressions 1.36 × 10 -9 (T/300)-0.142 exp(3.41/T) and 8.49 × 10 -10 (T/300)0.0661 exp(-5.21/T)cm3 molecule -1 s-1, respectively, over the 10 to 400 K temperature range. These revised rate coefficient expressions imply an increase in the destruction of H3+ at temperatures that are typical of dense clouds (10-30 K) by a factor of 2.5 to 3.0.

Original languageEnglish (US)
Pages (from-to)278-290
Number of pages13
JournalJournal of Physical Chemistry A
Issue number1
StatePublished - Jan 14 2010

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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