Transition state spectroscopy on the Li-HF system

The transition state region of the Li-HF system is theoretically studied via infrared excitation of the ground state of the complex in the reactant valley. The absorption spectrum shows intense peaks for which LiF is produced with high efficiency (≈90%), while the reaction has a very low cross section during the collision at the same energies. The reason is that the resonances reached through optical excitation are in the vicinity of the transition state.