Reactions of hydrated electrons (H₂O)_n^- with carbon dioxide and molecular oxygen: Hydration of the CO₂ ^- and O₂^- ions

The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO₂ and O₂ react efficiently with (H₂O)_n^- because they possess low-lying empty π* orbitals. The molecular CO₂^- and O₂^- anions are concurrently solvated and stabilized by the water ligands to form CO₂^-(H₂O) _n and O₂^-(H₂O)_n. Core exchange reactions are also observed, in which CO₂^-(H ₂O)_n is transformed into O₂^-(H ₂O)_n upon collision with O₂. This is in agreement with the prediction based on density functional theory calculations that O₂^-(H₂O)_n clusters are thermodynamically favored with respect to CO₂^-(H ₂O)_n. Electron detachment from the product species is only observed for CO₂^-(H₂O)₂, in agreement with the calculated electron affinities and solvation energies.