Isotopic effects in the interaction of ${\mathrm{O}}^{\ensuremath{-}}$ with ${\mathrm{D}}_{2}$ and ${\mathrm{H}}_{2}$ at low temperatures

Isotopic effects in the interaction of $O^{-}$ with $D_{2}$ and $H_{2}$ at low temperatures

Radek Plašil, Thuy Dung Tran, Štěpán Roučka, Pavol Jusko, Dmytro Mulin, Illia Zymak, Serhiy Rednyk, Artem Kovalenko, Petr Dohnal, Juraj Glosík, Karel Houfek, Jiří Táborský, and Martin Čížek

Phys. Rev. A 96, 062703 – Published 7 December 2017

Abstract

The isotopic effects in reactions of $O^{-}$ ions with $H_{2}$ and $D_{2}$ have been studied experimentally using a cryogenic 22-pole radio-frequency ion trap. The rate coefficients for associative detachment leading to $H_{2} O + e^{-}$ and to $D_{2} O + e^{-}$ and for atom transfer reactions leading to formation of ${OH}^{-}$ and ${OD}^{-}$ ions were determined at temperatures ranging from 15 to 300 K. The measured temperature dependencies of the rate coefficients for both channels of reactions of $O^{-}$ with $H_{2}$ and $D_{2}$ are compared with the results of the classical trajectory Monte Carlo simulation of the $O^{-} + H_{2}$ and $O^{-} + D_{2}$ collisions using the newly calculated potential energy surfaces. The measured temperature dependencies of the reaction rate coefficients for associative detachment are in very good agreement with the calculated ones. Agreement between experimental and calculated temperature dependencies of the rate coefficients of atom transfer reactions is off at most by a factor of 3 and the isotope effect is reproduced.