Double Rydberg anions, Rydberg radicals and micro-solvated cations with ammonium-water kernels.

Highly accurate ab initio electron-propagator and coupled-cluster methods are employed to predict the vertical electron attachment energies (VEAEs) of NH 4 + (H 2 O) n ( n = 1-4) cationic clusters. The VEAEs decrease with increasing n and the corresponding Dyson orbitals are diffused over peripheral, non-hydrogen bonded protons. Clusters formed from NH 4 - double Rydberg anions (DRAs) and stabilized by hydrogen bonding or electrostatic interactions are studied through calculations on NH 4 - (H 2 O) n complexes and are compared with more stable H - (NH 3 )(H 2 O) n isomers. Structures that have cationic and anionic congeners have notable changes in geometry. For all values of n , the hydride-molecule complex H - (NH 3 )(H 2 O) n is always the most stable, with large vertical electron detachment energies (VEDEs). NH 4 - (H 2 O) n DRA isomers are predicted to have VEDEs that correspond to energetically well-separated peaks in an anion photoelectron spectrum. Less stable DRA isomers display proton donation from the tetrahedral NH 4 - fragment to water molecules and VEDEs close to those of previously discovered DRAs. The most stable DRA isomers feature tetrahedral NH 4 - fragments without H bridges to water molecules and VEDEs that increase with n . Dyson orbitals of NH 4 - (H 2 O) n DRAs occupy regions beyond the exterior non-bridging O-H and N-H bonds. Thus, the Rydberg electrons in the uncharged Rydberg radicals and DRAs are held near the outer protons of the water and ammonia molecules. Several bound low-lying excited states of the doublet Rydberg radicals have single electrons occupying delocalized Dyson orbitals of s-like, p-like, d-like, or f-like nodal patterns with the following Aufbau principle: 1s, 1p, 1d, 2s, 2p, 1f.