Li(OH2)1,2-: Two double-Rydberg anion (DRA) derivatives of OH3- and O2H5

For several years, experimentalists have been searching for the double-Rydberg anions (DRAs), OH3- and O2H5-; however, no positive results have been reported other than those due to their theoretical prediction. By substituting one H atom in OH3- and O2H5- with an Li atom, we have successfully characterized the DRA's, Li(OH2)1,2- via anion photoelectron spectroscopy and ab initio calculations. The photoelectron spectra of [Li(OH2)1,2]- exhibited peaks with vertical detachment energy values at lower electron binding energies (EBE) than that of atomic Li-. Those observations showed that these anions are not the simple solvation complexes, Li-(H2O)1,2. Instead, their sharp, dominant peaks at EBE = 0.56 eV indicated that these are double-Rydberg anions. The geometrical structures and relevant Dyson orbitals, determined via our combined experimental and computational results, further demonstrated that these are the double-Rydberg anions, Li(OH2)1,2-. In LiOH2-, the Li atom and the H atoms are bound to the O atom, resulting in a pyramidal structure that resembles the predicted structure of OH3-. Moreover, Li(OH2)2- has the connectivity, H2O-Li-OH2-, with a bent O-Li-O sub-structure that resembles the predicted structure of O2H5-.