The Electron-pair Density Distribution of the ${}^{1,3}{\Pi }_u$ Excited States of H${}_2$

Abstract

The non-monotonic behavior of the electron repulsion energy and the interelectronic distance, as a function of the internuclear separation, in the ${}^3{\Pi }_u$ excited state of the hydrogen molecule has been assessed by explicitly calculation and analysis of the electron-pair density distribution functions from high level ab initio Full Configuration Interaction wave functions, for both the ${}^3{\Pi }_u$ and the ${}^1{\Pi }_u$ states. Additionally, the Hund's rule as applied to these two states has been accounted for in terms of simple electronic shielding effects induced by wave function antisymmetrization.

11 pages, 4 figures