What is it about?
The positively charged ammonium ion that occurs in many common salts and their solutions can bind two extra negatively charged electrons in a diffuse orbital to form a negative ion whose tetrahedral structure resembles that of methane. When an ammonium cation forms hydrogen bonds with ammonia molecules, two extra diffuse electrons can surround the entire assembly. Quantum mechanical calculations provide a complete assignment of the spectra that are associated with detachment of electrons by photons of light from these anions.
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Why is it important?
Electron pairs in molecules usually occur in chemical bonds between atoms or are confined to space near a single atom. Diffuse electron pairs are fundamentally different, for they are distributed over the periphery of an entire molecular positive ion. They are potentially useful in chemical reactions in which donation of electrons by a molecule must be accomplished without major disruption of the donor's structure of bonds.
Perspectives
Part of the satisfaction of writing this article in collaboration with Manuel Diaz Tinoco arose from the close and complete agreement between his calculations and the experiments performed in the laboratory of Kit Bowen at Johns Hopkins University. This confirmation of the concept of a Double Rydberg Anion further establishes the existence of a new kind of electron pair that extends traditional concepts of molecular structure and bonding.
Ruth W. Molette Professor Joseph Vincent Ortiz
Auburn University
Read the Original
This page is a summary of: Double Rydberg anions with solvated ammonium kernels: Electron binding energies and Dyson orbitals, The Journal of Chemical Physics, August 2019, American Institute of Physics,
DOI: 10.1063/1.5113614.
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