Electron-pair momentum densities of group 14, 15, and 16 atoms in their low-lying electronic states

摘要

Electron-pair intracule (relative motion) h(#upsilon#) and extracule (center-of-mass motion) d(P) densities in momentum space are studied for the ~3P, ~1D, and ~1S terms of five group 14 atoms with p~2 configurations, the ~4S, ~2D, and ~2P terms of five group 15 atoms with p~3 configurations, and the ~3P, ~1D, and ~1S terms of five group 16 atoms with p~4 configurations. Common to all fifteen atoms, the intracule densities show that a low energy term has a greater probability of finding a pair of electrons with a large relative momentum v than a high energy term. The Fermi hole effect in a high spin term appears naively in momentum space, and the average relative momentum <#upsilon#> is larger in a high angular momentum term. For the terms arising form the P~m electronic configurations (m = 2-4), the differences in the radial extracule densities are found to be almost isomorphic with the corresponding intracule ones. In a term with a high angular momentum, the average center-of-mass momentum

of an electron pair is always larger, and two electrons are less likely to have opposite momenta. The major origin of these differences in the electron-pair motions to the relative stability of terms can be explained by a rigorous relation between the kinetic energy T_(np) and the second intracule <#upsilon#~2>_(np) and extracule _(np) moments of the valence np subshell.