Competition between the H- and D-atom transfer channels in the HO + HD reaction: reduced-dimensional quantum and quasi-classical studies.

The ion-molecule reaction between a water cation and a hydrogen molecule has recently attracted considerable interest due to its importance in astrochemistry. In this work, the intramolecular isotope effect of the HO + HD reaction is investigated using a seven-dimensional initial state-selected time-dependent wave packet approach as well as a full-dimensional quasi-classical trajectory method on a full-dimensional ab initio global potential energy surface. The calculated branching ratios for the formation of HO and HDOvia H- and D-transfer agree reasonably well with the experimental values. The preference to the formation of the HO product observed using the experiment at low collision energies is reproduced by theoretical calculations and explained by a one-dimensional effective potential model.