Ab Initio Insights into the Formation of Hydrated Dielectrons: Structure and Recombination Dynamics

molecular dynamics simulations. Our findings reveal that the recombination reaction leading to dielectron formation occurs exclusively from the singlet state, with the dielectron occupying a slightly larger cavity than the single electron. The potential of mean force for open-shell singlet electron pairs has a local minimum at a distance corresponding to a metastable state in which two electron cavities are separated by a single bridging water molecule. From this state, recombination to form dielectrons occurs by two distinct mechanisms: diffusive recombination and direct tunneling. These pathways have an approximately 1:1 branching ratio, a balance set by the symmetry of the local solvation environment. Diffusion occurs when both electrons experience similar, coupled solvation environments, while tunneling is triggered when asymmetric solvation destabilizes one electron, which then tunnels into the more stable cavity of the electron pair in a manner mediated by the bridging water molecule.