State to state to state dynamics of the D+H2 -->HD+H reaction: control of transition-state pathways via reagent orientation.

The influence of reagent rotation on the dynamics of the D+H2 -->HD+H reaction is studied. The state-resolved differential cross section is measured using the Rydberg-atom scheme in a crossed beam experiment. It is found that the H2 rotation has a strong influence on the results. This effect was traced to the selection of the quantum bottleneck states through reagent orientation, thus suggesting a novel strategy to control the transition-state pathways in direct chemical reactions.