Electron-pair densities of singly charged atoms

For the singly charged 53 cations from Li+ to Cs+ and 43 anions from H- to I- in their ground states, spherically averaged electron-pair intracule (relative-motion) density h(u), extracule (center-of-mass-motion) density d(R), and their moments [u(n)] and [R-n] an examined, where u and R are the interelectronic distance and the center-of-mass radius of a pair of electrons, respectively. The intracule and extracule densities of all the 96 ions are found to be monotonically decreasing functions, as for neutral atoms. Approximate relations d(R) congruent to 8 h(2 R) and [u(n)]/[R-n] congruent to 2(n) are confirmed to be valid for the charged atoms as well. (C) 1999 Elsevier Science B.V. All rights reserved.