Interaction of O− and H2 at low temperatures

Zero-Point-Energy Driven Isotopic Exchange of the [H3O]- anion Probed by Mid-Infrared Action Spectroscopy

We present the first observation of vibrational transitions in the [H3O]- anion, an intermediate in the anion-molecule reaction of water, H2O, and hydride, H-, using a laser-induced isotopic H/D exchange reaction action spectroscopy scheme applied to anions. The observed bands are assigned as the fundamental and first overtone of the H2O-H- vibrational stretching mode, based on anharmonic calculations within the vibrational perturbation theory and vibrational configuration interaction. Although the D2O·D- species has the lowest energy, our experiments confirm the D2O·H- isotope to be a sink of the H/D exchange reaction. Ab initio calculations corroborate that the formation of D2O·H- is favored, as the zero-point-energy difference is larger between D2 and H2 than between D2O·H- and D2O·D-.

Ground-State Pd Anions React with H2 Much Faster than the Excited Pd Anions

Recent advances in experimental techniques have made it relatively easy to prepare reactant cations in well-defined states of electronic excitation. Extensive studies on the role of excited states in the cation-neutral reactions have contributed significantly to our understanding of reaction kinetics and dynamics. The excited states are often more reactive than the ground state. However, the reactions involving the excited atomic anion are very rare because the negative ions usually have no bound excited states. In the present work, we report the state-specific reaction of Pd anions with H₂. Surprisingly, we observed that the ground-state Pd anions react with H₂ 10 times faster than the excited Pd anions. The high-level calculations show that the difference is due to the reaction barrier.

H/D exchange in reactions of OH− with D2 and of OD− with H2 at low temperatures

The H₃O⁻ isotopic system was studied by observing the endothermic and exothermic isotope exchange reactions OD⁻ + H₂ → OH⁻ + HD and OH⁻ + D₂ → OD⁻ + HD using a cryogenic ion trap.