Dynamics of the isotope exchange reaction of D with H3+, H2D+, and D2H+
(2021) Journal of Chemical Physics — Vol. 154, n° 8, p. 84307 (2021)
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- Authors
Bowen, K. P. 
Hillenbrand, P.-M. Liévin, J. Savin, D. W.
- Abstract
- We have measured the merged-beams rate coefficient for the titular isotope exchange reactions as a function of the relative collision energy in the range of ∼3 meV to 10 eV. The results appear to scale with the number of available sites for deuteration. We have performed extensive theoretical calculations to characterize the zero-point-energy corrected reaction path. Vibrationally adiabatic minimum energy paths were obtained using a combination of UQCISD and ic- MRCI calculations. The resulting barrier height, ranging from 68 meV to 89 meV, together with the various asymptotes that may be reached in the collision, were used in a classical over-the-barrier model. All competing endoergic reaction channels were taken into account using a flux reduction factor. This model reproduces all three experimental sets quite satisfactorily. In order to generate thermal rate coefficients down to 10 K, the internal excitation energy distribution of each H+3 isotopologue is evaluated level by level using available line lists and accurate spectroscopic parameters. Tunneling is accounted for by direct inclusion of the exact quantum tunneling probability in the evaluation of the cross section. We derive a thermal rate coefficient of < 1×10−12 cm3 s−1 for temperatures below 44, 86, and 139 K for the reaction of D with H+3 , H2D+, and D2H+, respectively, with tunneling effects included. The derived thermal rate coefficients exceed the RPMD prediction of Bulut et al. [J. Phys. Chem. A 123, 8766 (2019)] at all temperatures.
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Citations
Bowen, K. P., Hillenbrand, P.-M., Liévin, J., Savin, D. W., & Urbain, X. (2021). Dynamics of the isotope exchange reaction of D with H3+, H2D+, and D2H+. Journal of Chemical Physics, 154(8), 84307. https://doi.org/10.1063/5.0038434 (Original work published 2021)