A double Rydberg anion with a hydrogen bond and a solvated double Rydberg anion:: Interpretation of the photoelectron spectrum of N2H7-

A double Rydberg anion has two electrons in diffuse orbitals that are bound by a closed-shell, cationic core. Low-energy features in the recently reported photoelectron spectrum of N2H7- are assigned to double Rydberg anions on the basis of electron propagator calculations employing Brueckner doubles, coupled-cluster reference states. The lowest electron detachment energy, 0.415 eV, corresponds to an initial state consisting of a hydrogen-bridged N2H7+ core and two diffuse electrons. A feature at slightly higher energy, 0.578 eV, belongs to a complex that comprises a tetrahedral NH4- double Rydberg anion and an ammonia solvent molecule. The most intense peak in the photoelectron spectrum, which occurs at 1.460 eV, pertains to a complex with a hydride anion and two ammonia solvent molecules. Plots of Dyson orbitals associated with electron detachment energies facilitate qualitative interpretation of electronic structure in the anions and in the neutral final states. Vibrational structure associated with each of these features has been interpreted as well. Previous assignments of electron detachment energies to the hydride-ammonia and tetrahedral isomers of NH4- have been confirmed with the present methods. Vibrationally excited final states have been assigned for this spectrum also. (C) 2002 American Institute of Physics.