Isotopic and quantum-rovibrational-state effects for the ion–molecule reaction in the collision energy range of 0.03–10.00 eV
We report detailed quantum-rovibrational-state-selected integral cross sections for the formation of H3O+via H-transfer (σHT) and H2DO+via D-transfer (σDT) from the reaction in the center-of-mass collision energy (Ecm) range of 0.03–10.00 eV, where (v+1v+2v+3) = (000), (100), and (020) and . The Ecm inhibition and rotational enhancement observed for these reactions at Ecm < 0.5 eV are generally consistent with those reported previously for H2O+ + H2(D2) reactions. However, in contrast to the vibrational inhibition observed for the latter reactions at low Ecm < 0.5 eV, both the σHT and σDT for the H2O+ + HD reaction are found to be enhanced by (100) vibrational excitation, which is not predicted by the current state-of-the-art theoretical dynamics calculations. Furthermore, the (100) vibrational enhancement for the H2O+ + HD reaction is observed in the full Ecm range of 0.03–10.00 eV. The fact that vibrational enhancement is only observed for the reaction of H2O+ + HD, and not for H2O+ + H2(D2) reactions suggests that the asymmetry of HD may play a role in the reaction dynamics. In addition to the strong isotopic effect favoring the σHT channel of the H2O+ + HD reaction at low Ecm < 0.5 eV, competition between the σHT and σDT of the H2O+ + HD reaction is also observed at Ecm = 0.3–10.0 eV. The present state-selected study of the H2O+ + HD reaction, along with the previous studies of the H2O+ + H2(D2) reactions, clearly shows that the chemical reactivity of H2O+ toward H2 (HD, D2) depends not only on Ecm, but also on the rotational and vibrational states of H2O+(X2B1). The detailed σHT and σDT values obtained here with single rovibrational-state selections of the reactant H2O+ are expected to be valuable benchmarks for state-of-the-art theoretical calculations on the chemical dynamics of the title reaction.